objective-c代碼學(xué)習(xí)大綱

Objective-C代碼學(xué)習(xí)大綱(1)2011-05-1114:06佚名otierney我要評論(4)字號:TT

收藏本文為臺灣出版的《Objective-C學(xué)習(xí)大綱》的翻譯文檔,系統(tǒng)介紹了Objective-C代碼,很多名詞為臺灣同胞特指詞匯,在學(xué)習(xí)時仔細研讀才能體會。AD：2013大數(shù)據(jù)全球技術(shù)峰會低價搶票中所有這篇初學(xué)者指南的源始碼都可以由objc.tar.gz下載。這篇教學(xué)中的許多範例都是由SteveKochan在ProgramminginObjective-C.ー書中撰寫。如果你想得到更多詳細資訊及範例,請直接參考該書。這個網(wǎng)站上登載的所有範例皆經(jīng)過他的允許,所以請勿復(fù)製轉(zhuǎn)載。設(shè)定環(huán)境Linux/FreeBSD:安裝GNUStep為了編譯GNUstep應(yīng)用程式,必須先執(zhí)行位于/usr/GNUstep/System/Makefiles/GNUstep.sh的GNUstep.sh這個檔案。這個路徑取決于你的系統(tǒng)環(huán)境,有些是在/usr,some/usr/lib,有些是/usr/localo如果你的shell是以csh/tcsh為基礎(chǔ)的shell,則應(yīng)該改用GNUStep.csho建議把這個指令放在.bashrc或,cshrc中。MacOSX:安裝XCodeWindowsNT5.X:安裝cygwin或mingw?然后安裝GNUStep

前百這篇教學(xué)假設(shè)你已經(jīng)有一些基本的c語言知識,包括C資料型別、什么是函式、什么是回傳值、關(guān)于指標的知識以及基本的C語言記憶體管理。如果您沒有這些背景知識,我非常建議你讀ー讀K&R的書:TheCProgrammingLanguage（譯注:臺灣出版書名為C程式語言第二版）這是C語言的設(shè)計者所寫的書。Objective-C?是C的衍生語言,繼承了所有C語言的特性。是有一些例外,但是它們不是繼承于C的語言特性本身。nil：在C/C++你或許曾使用過NULL,而在Objective-C中則是nil。不同之處是你可以傳遞訊息給nil（例如[nilmessage];）?這是完全合法的,然而你卻不能對NULL如法炮製。BOOL：C沒有正式的布林型別,而在Objective-C中也不是「真的」有。它是包含在Foundationclasses（基本類別庫）中（即importNSObject.h;nil也是包括在這個標頭檔內(nèi)）。BOOL在Objective-C中有兩種型態(tài)：YES或N0,而不是TRUE或FALSE〇#importvsttinclude:就如同你在helloworld範例中看到的，我們使用了#importoftimport由gcc編譯器支援。我并不建議使用ttinclude,#import基本上跟,h檔頭尾的ttifndef#define#endif相同。許多程式員們都同意,使用這些東西這是十分愚蠢的。無論如何,使用#timport就對了。這樣不但可以避免麻煩,而且萬一有一天gcc把它拿掉了,將會有足夠的Objective-C程式員可以堅持保留它或是將它放冋來。偷偷告訴你，Apple在它們官方的程式碼中也使用了#importB所以萬一有一天這種事真的發(fā)生,不難預(yù)料Apple將會提供ー個支援ftimport的gcc分支版本。在Objective-C中,method及message這兩個字是可以互換的。不過messages擁有特別的特性,ー個message可以動態(tài)的轉(zhuǎn)送給另ー個物件。在Objective-C中，嗯叫物件上的ー個訊息并不一定表示物件真的會實作這個訊息,而是物件知道如何以某種方式去實作它,或是轉(zhuǎn)送給知道如何實作的物件。編譯helloworldhello.m#main(intargcrconstchar*argv[]){.printf("hell〇world\nn);.return0;}輸出helloworld在Objective-C中使用#import代替#includeObjective-C的預(yù)設(shè)副檔名是.m

Objective-C代碼學(xué)習(xí)大綱(2)2011-05-1114:06佚名otierney我要評論(4)字號:TT

收藏Q本文為臺灣出版的《Objective-C學(xué)習(xí)大綱》的翻譯文檔,系統(tǒng)介紹了Objective-C代碼,很多名詞為臺灣同胞特指詞匯,在學(xué)習(xí)時仔細研讀才能體會。AD：2013大數(shù)據(jù)全球技術(shù)峰會低價搶票中創(chuàng)建classes?interface..Fraction.h.#import.@interfaceFraction:NSObject{.intnumerator;intdenominator;}. -(void)print;--(void)setNumerator:(int)n;-(void)setDenominator:(int)d;-(int)numerator;. -(int)denominator;.@endNSObject：NeXTStepObject的縮寫。因為它已經(jīng)改名為OpenStep,所以這在今天已經(jīng)不是那么有意義了。繼承(inheritance)以Class:Parent表示,就像上面的Fraction:NSObject〇夾在@interfaceClass:Parent{....}中的稱為instancevariableso沒有設(shè)定存取權(quán)限(protected,public,private)時,預(yù)設(shè)的存取權(quán)限為protectedo設(shè)定權(quán)限的方式將在稍后說明。Instancemethods跟在成員變數(shù)(即instancevariables)后。格式為:scope(returnType)methodName:(parameterIType)parameterIName;scope有class或instance兩種。1nstancemethods以ー開頭,classlevelmethods以+開頭。Interface以一?個@end作為結(jié)束。?implementation.Fraction.m.

#import@implementationFraction(void)print{. printf(n%i/%iM,numeratorrdenominator);TOC\o"1-5"\h\z). -(void)setNumerator: (int) n {. nnumerator=n;. }. -(void)setDenominator: (int) d{. ddenominator=d;}. -(int) denominator {. return denominator;. }. "(int) numerator {. return numerator;). @endImplementation以?implementationClassName開始,以@end結(jié)束。Implementation以4..9.101112131415161718192021222324252627282930313233343536373839Implement定義好的methods的方式,跟在interface中宣告時很近似。把它們湊在ー起main.m.#import..#importnFraction.hintmain(intargc,constchar*argv[]){//createanewinstanceinit];Fraction*fracinit];//setthevalues.[fracsetNumerator:1];[fracsetDenominator:3];//printitprintf("Thefractionis:”);[fracprint];.. printf(“ヽn");//freememory[fracrelease];return0;}outputThefractionis:1/33.Fraction*frac[[Fractionalloc]init];這行程式碼中有很多重要的東西。在Objective-C中惣叫methods的方法是[objectmethod],就像C++的object-〉method()。Objective-C沒有value型別。所以沒有像C++的Fractionfrac;frac.print():這類的東西。在Objective-C中完全使用指標來處理物件。這行程式碼實際上做了兩件事:[Fractionalloc]嗯叫了Fractionclass的allocmethodo這就像malloc記憶體,這個動作也做了一樣的事情。[objectinit]是ー個建構(gòu)子(constructor)惣叫,負責(zé)初始化物件中的所有變數(shù)。它惣叫了[Fractionalloc]傳回的instance上的initmethodo這個動作非常普遍,所以通常以一行程式完成:Object*var=[[Objectalloc]init];[fracsetNumerator:1]非常簡單。它嗯叫了frac上的setNumeratormethod并傳入1為參數(shù)。如同每個C的變體,Objective-C也有一個用以釋放記憶體的方式：releaseo它繼承自NSObject,這個method在之后會有詳盡的解說。Objective-C代碼學(xué)習(xí)大綱(3)2011-05-1114:06佚名otierney我要評論(4)字號:TT本文為臺灣出版的《Objective-C學(xué)習(xí)大綱》的翻譯文檔,系統(tǒng)介紹了Objective-C代碼,很多名詞為臺灣同胞特指詞匯,在學(xué)習(xí)時仔細研讀才能體會。AD：2013大數(shù)據(jù)全球技術(shù)峰會低價搶票中詳細說明...多重參數(shù)目前為止我還沒展示如何傳遞多個參數(shù)。這個語法乍看之下不是很直覺,不過它卻是來自一個十分受歡迎的Smalltalk版本。Fraction,h.....-(void)setNumerator:(int)nandDenominator:(int)d;.....Fraction.m??.. -(void)setNumerator:(int)nandDenominator:(int)d{. nnumerator=n;. ddenominator=d;}.... main.m.#import

2627282930313233343536373839404142434445464748495051525354555657585960616263646566676869?import"Fraction.hnintmain(intargc,constchar*argv[]){//createanewinstanceFraction*frac=[[Fractionalloc]init];Fraction*frac2=[[Fractionalloc]init];//setthevalues[fracsetNumerator:1];[fracsetDenominator:3];//combinedset[frac2setNumerator:1andDenominator:5];//printitprintf("Thefractionis:");[fracprint];printf("\n");//printitprintf("Fraction2is:");[frac2print];printf("\n");//freememory[fracrelease];[frac2release];return0;

}outputThefractionis:1/3.Fraction2is:1/5這個method實際上叫做setNumerator:andDenominator:加入其他參數(shù)的方法就跟加入第二個時一樣,即method:label1:label2:label3:,而惣叫的方法是[objmethod:param1label1:param2label2:param3label3:param4]Labels是非必要的,所以可以有一個像這樣的method：method:::,簡單的省略label名稱,但以:區(qū)隔參數(shù)。并不建議這樣使用。建構(gòu)子(Constructors)!,Fraction.h.......-(Fraction*)initWithNumerator:(int)ndenominator:(int)d;.フ????.Fraction.m??.. -(Fraction*)initWithNumerator:(int)ndenominator:(int)d{.self[superinit]self[superinit];

17.18.if(self){19.20.[selfsetNumerator:nandDenominator:d];21.22.}23.24.returnself;25.26.}27.28.???29.30.main.m31.32.#import33.34.?importnFraction.h,main(intargc,constchar*argv[]){37.38.//createanewinstance39.40.Fraction*frac=[[Fractionalloc]init];41.42.Fraction*frac2=[[Fractionalloc]init];43.Fraction*frac3=[[Fractionalloc]initWithNumerator:344.denominator:10];45.46.//setthevalues47.48.[fracsetNumerator:1];49.50.[fracsetDenominator:3];51.52.//combinedset53.54.[frac2setNumerator:1andDenominator:5];55.56.//printit57.58.printf("Thefractionis:");59.[fracprint];

6〇,61.printf(M\nn);62.63.printf("Fraction2is:n)；64.65.[frac2print];66.67.printf(n\nn);68.69.printf("Fraction3is:”)；70.71.[frac3print];72.73.printf("\n");74.75.//freememory76.77.[fracrelease];78.79.[frac2release];80.81.[frac3release];82.83.return0;84.85.}outputThefractionis:1/3.Fraction2is:1/5.Fraction3is:3/10?interface裡的宣告就如同正常的函式。?implementation使用了一個新的關(guān)鍵字:super如同Java,Objective-C只有一個parentclass(父類別)。使用［superinit］來存取Superconstructor?這個動作需要適當?shù)睦^承設(shè)計。你將這個動作回傳的instance指派給另一新個關(guān)鍵字:self。Self很像C++與Java的this指標。if(self)跟(self!=nil)ー樣,是為了確定superconstructor成功傳回了一個新物件。nil是Objective-C用來表達C/C++中NULL的方式,可以引入NSObject來取得。當你初始化變數(shù)以后,你用傳回self的方式來傳回自己的位址。預(yù)設(shè)的建構(gòu)子是-(id)inito技術(shù)上來說,Objective-C中的建構(gòu)子就是ー個"init"method,而不像C++與Java有特殊的結(jié)構(gòu)。存取權(quán)限預(yù)設(shè)的權(quán)限是0protectedJava實作的方式是在methods與變數(shù)前面加上public/private/protected修飾語,而Objective-C的作法則更像C++對于instancevariable(譯注:C++術(shù)語一般稱為datamembers)的方式。!,Access,h#import.@interfaceAccess:NSObject{.@public

9.intpublicVar;10.11.12.@privateVar;15.16.intprivateVar2;17.18.@protectedVar;21.22.}23.24.@end25.26.Access.m27.28.#import"Access.hn29.30.@implementationAccess31.32.@end33.34.main.m35.36.#import"Access.hn37.38.?main(intargc,constchar*argv[]){41.42.Access*a=[[Accessalloc]init];43.44.//works45.46.a->publicVar=5;47.48.printf("publicvar:%i\n"za->publicVar);49.50.//doesn1tcompile51.//a->privateVar=10;. //printf("privatevar:%i\nnra->privateVar);[arelease];. return0;)outputpublicvar:5如同你所看到的,就像C++中private:[listofvars]public:[listofvars]的格式,它只是改成了@private,?protected,等等。ClasslevelaccessClassA.h.,#import.staticintcount;.@interfaceClassA:NSObject..+(int)initCount;+(void)initialize;@end.ClassA.m. #import"ClassA.hH@implementation ClassA-(id)init{. self=[superinit];

2425242526272829303132333435363738394041424344454647484950515253545556575859returnself;}+(int)initCount{returncount;}+(void)initialize{count=0;)@endmain.m#import"ClassA.hH#importintmain(intargc,constchar*argv[]){ClassA*cl=[[ClassAalloc]init];ClassA*c2=[[ClassAalloc]init];//printcount606162636465ClassA*c3[[ClassAalloc]init];//printcountagainprintf("ClassAcount:%i\n”,606162636465ClassA*c3[[ClassAalloc]init];//printcountagainprintf("ClassAcount:%i\n”,[ClassAinitCount]);[clrelease];[c2release];[c3release];return0;.}output.ClassAcount:2..ClassAcount:3staticintcount=0;這是classvariable宣告的方式。其實這種變數(shù)擺在這裡并不理想,比較好的解法是像Java實作staticclassvariables的方法。然而,它確實能用。+(int)initCount:這是回傳count值的實際methodo請注意這細微的差別!這裡在type前面不用減號一而改用加號+。加號+表示這是ー個classlevelfunction。(譯注:許多文件中,classlevelfunctions被稱為classfunctions或classmethod)存取這個變數(shù)跟存取一般成員變數(shù)沒有兩樣,就像ClassA中的count++用法。+(void)initializemethodis在Objective-C開始執(zhí)行你的程式時被惣叫,而且它也被每個class惣叫。這是初始化像我們的count這類classlevelvariables的好地方

..9.1011121314151617181920212223242526272829303132333435363738異常情況(Exceptions)注意:異常處理只有MacOSX10.3以上オ支援。CupWarningException.h#import@interfaceCupWarningException:NSException@endCupWarningException.m. #importHCupWarningException.hH. @implementationCupWarningException. @end. CupOverflowException.h. #import. @interfaceCupOverflowException:NSException. @end. CupOverflowException.m. #importMCupOverflowException.hM. @implementationCupOverflowException. @endCup?h#import@interfaceCup:NSObject{

39.40.intlevel;41.42.)43.44.-(int)level;8.-(void)setLevel:(int)1;-(void)fill;49.50.-(void)empty;51.52.-(void)print;53.54.@end55.56.Cup.m0.#importnCup.hM?importnCupOverflowException.hH61.62.?import"CupWarningException.h"63.64.?import8.69.70.?import@implementationCup-(id)init{71.72.self=[superinit];73.74.if(self){75.76.[selfsetLevel:0];77.78.}2.returnself;}83.84.-(int)level{85.86.returnlevel;87.88.}89.90.-(void)setLevel:(int)1{91.92.llevel=1;93.94.if(level>100){95.96.//throwoverflow97.98.NSException*e=[CupOverflowException99.100.exceptionWithName:@HCupOverflowExceptionn101.102.reason:@"Thelevelisabove100n103.104.userlnfo:nil];105.106.@throwe;107.108.}elseif(level>=50){109.110.//throwwarning111.112.NSException*e=[CupWarningException113.114.exceptionWithName:@MCupWarningExceptionn115.116.reason:@"Thelevelisaboveorat50"117.118.userinfo:nil];119.120.@throwe;121.122.}elseif(level<0){123.124.//throwexception125.126.NSException*e=[NSException127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170exceptionWithName:@MCupUnderflowException11reason:@"Thelevelisbelow〇”userinfo:nil];@throwe;})(void)fill{[selfsetLevel:level+10];}(void)empty{[selfsetLevel:level-10];}(void)print{printf("Cuplevelis:%i\n",level);}@endmain.m#import"Cup.h"import"CupOverflowException.h"import"CupWarningException.h"import?import

171.#import172.173.#main(intargc,constchar*argv[]){176.177.NSAutoreleasePool*pool=[[NSAutoreleasePool]init];178.179.Cup*cup=[[Cupalloc]init];180.181.inti;182.183.//thiswillwork184.185.for(i=0;i<4;i++){186.187.[cupfill];188.189.[cupprint];190.191.}192.193.//thiswillthrowexceptions194.195.for(i=0;i<7;i++){196.197.@try(198.199.[cupfill];200.201.}@catch(CupWarningException*e){202.203.printf("％s:",[[ename]cString]);204.205.}@catch(CupOverflowException*e){206.207.printf("%s:",[[ename]cString]);208.209.}@finally{210.211.[cupprint];212.213.}alloc17.217.//throwagenericexception19.220.@try{[cupsetLevel:-1];}@catch(NSException*e){[ereason]printf("％s:%s\n”，[[ename]cString],[[ereason]cString]);}//freememory[cuprelease];[poolrelease];.}output1.Cuplevelis:102.3.Cuplevelis:204.5.Cuplevelis:306.7.Cuplevelis:408.9.CupWarningException:Cuplevelis:5010.11121314151617CupWarningException:Cuplevelis:CupWarningException:Cuplevelis:CupWarningException:Cuplevelis:CupWarningException:Cuplevelis:60708090CupWarningExceptionCupWarningException:Cuplevelis:100CupOverflowException:Cuplevelis:110. CupUnderflowException:Thelevelisbelow0NSAutoreleasePool是ー個記憶體管理類別?，F(xiàn)在先別管它是干嘛的。Exceptions(異常情況)的丟出不需要擴充(extend)NSException物件,你可簡單的用id來代表它:?catch(ide){...}還有一個finally區(qū)塊,它的行為就像Java的異常處理方式,finally區(qū)塊的內(nèi)容保證會被惣叫。Cup.m裡的0/?CupOverflowException?是ー個NSString常數(shù)物件。在Objective-C中,?符號通常用來代表這是語言的衍生部分。C語言形式的字串(Cstring)就像C/C++ー樣是"Stringconstant"的形式,型別為char*oObjective-C代碼學(xué)習(xí)大綱(4)2011-05-1114:06佚名otiemey我要評論(4)字號:TlT

收藏エ3 4- Iロ F本文為臺灣出版的《Objective-C學(xué)習(xí)大綱》的翻譯文檔,系統(tǒng)介紹了 :Objective-C代碼,很多名詞為臺灣同胞特指詞匯,在學(xué)習(xí)時仔細研讀才能j體會。 :AD：2013大數(shù)據(jù)全球技術(shù)峰會低價搶票中セ繼承、多型(Inheritance,Polymorphism)以及其他物件導(dǎo)向功能id型別Objective-C有種叫做id的型別,它的運作有時候像是void*,不過它卻嚴格規(guī)定只能用在物件。Objective-C與Java跟C++不ー樣,你在嗯叫ー個物件的method時,并不需要知道這個物件的型別。當然這個method一定要存在,這稱為Objective-C的訊息傳遞。!,Fraction?h..#import.@interfaceFraction:NSObject{intnumerator;intdenominator;}-(Fraction*)initWithNumerator:(int)ndenominator:(int)d;.. -(void)print;. -(void)setNumerator:(int)d;-(void)setDenominator:(int)d;-(void)setNumerator:(int)nandDenominator:(int)d；. -(int)numerator;.-(int)denominator;@end

29.Fraction.m.?importHFraction.hn?import@implementationFraction-(Fraction*)initWithNumerator:(int)ndenominator(int)d(self=[superinit];if(self){[selfsetNumerator:nandDenominator:d];.)returnself;}-(void)print{printf(n%i/%inznumerator,denominator);...}(void)setNumerator:(int)nnnumerator=n;}(void)setDenominator:(int)ddenominator=d;}(void)setNumerator:(int)n{d(andDenominator:(int)d{71.72.nnumerator=n;73.74.ddenominator=d;75.76.}77.78.-(int)denominator{79.80.returndenominator;81.82.)83.84.-(int)numerator{85.86.returnnumerator;87.88.}89.90.@end91.92.Complex.h93.94.#import95.96.@interfaceComplex:NSObject{97.98.doublereal;99.100.doubleimaginary;101.102.}103.-(Complex*)initWithReal:(double)randlmaginary:(double)i;104.105.106.-(void)setReal:(double)r;107.108.-(void)setImaginary:(double)i;109.i；110.-(void)setReal:(double)randlmaginary:(double)111.112.-(double)real;113.114.-(double)imaginary;115.116.-(void)print;117.118.@end22.Complex,m#import"Complex.h"123.124.#import125.126.@implementationComplex127.-(Complex*)initWithReal:(double)randlmaginary:(double)i{34.135.136.self=[superinit];if(self){[selfsetReal:randlmaginary:i];)40.141.142.returnself;}-(void)setReal:(double)r{143.144.rreal=r;145.146.}147.148.-(void)setImaginary:(double)i{149.150.iimaginary=i;151.152.153.i(}-(void)setReal:(double)randlmaginary:(double)

155.156.rreal=r;157.158.iimaginary=i;159.160.}161.162.-(double)real{163.164.returnreal;165.166.)167.168.-(double)imaginary{169.170.returnimaginary;171.172.}173.174.-(void)print{175.176.printf("%_f+%_fiM,real,imaginary);177.178.)179.180.@end181.182.main.m183.184.#import185.186.#import"Fraction.hn187.188.#import"Cmain(intargc,constchar*argv[]){191.192.//createanewinstance193.Fraction*frac=[[Fractionalloc]initWithNumerator:1194.denominator:10];195.Complex*comp=[[Complexalloc]initWithReal:10andlmaginary:15];

197.198.idnumber;199.200.//printfraction201.202.number=frac;203.204.printf("Thefractionis:");205.206.[numberprint];207.208.printf("\n");209.210.//printcomplex211.212.number=comp;213.214.printf("Thecomplexnumberis:");215.216.[numberprint];217.218.printf("\n");219.220.//freememory221.222.[fracrelease];223.224.[comprelease];225.226.return0;227.}outputThefractionis:1/10Thecomplexnumberis:10.000000+15.OOOOOOi這種動態(tài)連結(jié)有顯而易見的好處。你不需要知道你嗯叫method的那個東西是什么型別,如果這個物件對這個訊息有反應(yīng),那就會喚起這個methodo..9.1011121314151617181920212223242526272829303132333435這也不會牽涉到ー堆繁瑣的轉(zhuǎn)型動作,比如在Java裡嗯叫一個整數(shù)物件的,intValue()就得先轉(zhuǎn)型,然后才能惣叫這個methodo繼承(Inheritance)Rectangle.h#import@interfaceRectangle:NSObject{intwidth;intheight;}(Rectangle*)initWithWidth:(int)wheight:(int)h;(void)setwidth:(int)w;(void)setHeight:(int)h;(void)setwidth:(int)wheight:(int)h;(int)width;(int)height;(void)print;@endRectangle.m#import"Rectangle?h”#import@implementationRectangle

36.37.-(Rectangle*)initWithWidth:(int)wheight:h{38.39.self=[superinit];40.41.if(self){42.43.[selfsetwidth:wheight:h];44.45.)46.47.returnself;48.49.}50.51.-(void)setwidth:(int)w{52.53.wwidth=w;54.55.}56.57.-(void)setHeight:(int)h{58.59.hheight=h;60.61.)62.63.-(void)setwidth:(int)wheight:(int)h{64.65.wwidth=w;66.67.hheight=h;68.69.}70.71.-(int)width{72.73.returnwidth;74.75.)76.77.-(int)height{78.(int)

79.80.returnheight;81.82.)83.84.-(void)print{85.printf("width=%i,height=%i”，width,height);86.87.88.)89.90.@end91.92.Square.h93.94.#import"Rectangle.h"95.96.@interfaceSquare:Rectangle97.98.-(Square*)initWithSize:(int)s;99.100.-(void)setSize:(int)s;101.102.-(int)size;103.104.@end105.106.Square.m107.108.#import"Square.h"109.110.@implementationSquare111.112.-(Square*)initWithSize:(int)s{113.114.self=[superinit];115.116.if(self){117.118.[selfsetSize:s];119.120.}121.returnself;122.123. )124.125.126.-(void)setsize:(int)s{127.128.width=s;129.130.height=s;131.132.}133.134.-(int)size{135.136.returnwidth;137.138.)139.140.-(void)setwidth:(int)w{141.142.[selfsetsize:w];143.144.}145.146.-(void)setHeight:(int)h{147.148.[selfsetsize:h];149.150.}151.152.@end153.154.main.m155.156.#importHSquare.hM157.158.?import"Rectangle.h"159.160.?main(intargc,constchar*argv[]){163.Rectangle*rec=[[Rectanglealloc]initWithWidth:10height:20];165.Square*sq=[[Squarealloc]initWithSize:166.167.//printem168.169.printf("Rectangle:");170.171.[recprint];172.173.printf("\n");174.175.printf("Square:");176.177.[sqprint];178.179.printf("\n");180.181.//updatesquare182.183.[sqsetwidth:20];184.185.printf("Squareafterchange:");186.187.[sqprint];188.189.printf("\n");190.191.//freememory192.193.[recrelease];194.195.[sqrelease];196.197.return0;198.199.}output15];Rectangle:width=10,height=20.Square:width=15,height=15Squareafterchange:width=20,height=20繼承在Objective-C裡比較像Java。當你擴充你的superclass(所以只能有一個parent)?你想自訂這個superclass的method?只要簡單的在你的childclassimplementation裡放上新的實作內(nèi)容即可。而不需要C++裡呆呆的virtualtable〇這裡還有一個值得玩味的地方,如果你企圖像這樣去惣叫rectangle的constructor：Square*sq=[[Squarealloc]initWithWidth:10height:15],會發(fā)生什么事?答案是會產(chǎn)生一個編譯器錯誤。因為rectangleconstructor回傳的型別是Rectangle*,而不是Square*,所以這行不通。在某種情況下如果你真想這樣用,使用id型別會是很好的選擇。如果你想使用parent的constructor,只要把Rectangle?回傳型別改成id即可。動態(tài)識別(Dynamictypes)這裡有一些用于Objective-C動態(tài)識別的methods(說明部分採中英并列,因為我覺得英文比較傳神,中文怎么譯都怪)：1.-(BOOL)isKindOfClass:classObjisobjectadescendentormemberofclassObj此物件是否是classObj的子孫或ー員1.-(BOOL)isMemberOfClass:classObjisobjectamemberofclassObj此物件是否是classObj的一員1.-(BOOL)respondsToSelector:selectordoestheobjecthaveamethodnamedspecifiecbytheselector此物件是否有叫做selector的method+(BOOL)instancesRespondToSelector:selectordoesanobjectcreatedbythisclasshavetheabilitytorespondtothespecifiedselector此物件是否是由有能力回應(yīng)指定selector的物件所產(chǎn)生-(id)performSelector:selectorinvokethespecifiedselectorontheobject喚起此物件的指定selector所有繼承自NSObject都有一個可回傳ー個class物件的classmethodo這非常近似于Java的getClass()methodo這個class物件被使用于前述的methods中。Selectors在Objective-C用以表示訊息。下ー個範例會秀出建立selector的語法。!,main.m..#importnSquare.hH..#import"Rectangle?h”.#main(intargc,constchar*argv[]){Rectangle*rec=[[Rectanglealloc]initWithWidth:10height:20];Square*sq=[[Squarealloc]initWithSize:15];.//isMemberOfClass. //true

192021222324252627282930313233343536373839404142434445464748495051525354555657YES)if([sqisMemberOfClass:[Squareclass]]printf(nsquareisamemberofsquareclass\nM);YES)}//falseif([sqisMemberOfClass:[Rectangleclass]]==YESprintf(Msquareisamemberofrectangleclass\nM))//falseif([sqisMemberOfClass:[NSObjectclass]]==YESprintf(Msquareisamemberofobjectclass\nM);}//isKindOfClass//trueif([sqisKindOfClass:[Squareclass]]==YES){printf(Msquareisakindofsquareclass\nn);}//trueif([sqisKindOfClass:[Rectangleclass]]==YES)printf(Msquareisakindofrectangleclass'n");

//trueif([sqisKindOfClass:[NSObjectclass]]==YES)(printf(Msquareisakindofobjectclass\nn);}//respondsToSelector//trueif([sqrespondsToSelector:@selector(setsize:)]==YES){printf(nsquarerespondstosetsize:method'n");}//falseif([sqrespondsToSelector:@selector(nonExistant)]==YES){printf(nsquarerespondstononExistantmethod"")J)IItrueif([SquarerespondsToSelector:?selector(alloc)]==YES){printf("squareclassrespondstoallocmethod\n")t}5859606162636465666768697071727374757677787980818283848586878889909192939495//instancesRespondToSelector//false7.square.square.square.square.squareif([RectangleinstancesRespondToSelector:@selector(setsize:)]==YES){98.99. printf(Hrectangleinstancerespondstosetsize:method\n”);03. //true104.if([SquareinstancesRespondToSelector:@selector(setSize:)]==YES){.printf(nsquareinstancerespondstosetSize:method\nM);}//freememory[recrelease];.[sqrelease];return0;118.)outputisamemberofsquareclassisakindofsquareclassisakindofrectangleclassisakindofobjectclassrespondstosetSize:methodsquareclassrespondstoallocmethodsquareinstancerespondstosetsize:methodCategories當你想要為某個class新增methods?你通常會擴充(extend,即繼承)它。然而這不一定是個完美解法,特別是你想要重寫ー個class的某個功能,但你卻沒有姬始碼時。Categories允許你在現(xiàn)有的class加入新功能,但不需要擴充它。Ruby語言也有類似的功能。FractionMath.h..#import"Fraction?h”..@interfaceFraction(Math).-(Fraction*)add:(Fraction*)f;.-(Fraction*)mul:(Fraction*)f;-(Fraction*)div:(Fraction*)f;-(Fraction*)sub:(Fraction*)f;.@endFractionMath.m. #import"FractionMath.h"@implementationFraction (Math)-(Fraction*)add:(Fraction*> f{.return[[Fractionalloc]initWithNumerator:numerator*[fdenominator]+. denominator*[fnumerator]9. denominator:denominator*[fdenominator]];30.

3132333435363738394041424344454647484950515253545556575859606162636465666768697071-(Fraction*)mul:(Fraction*)f{return[[Fractionalloc]initWithNumerator:numerator*[fnumerator]denominator:denominator*[fdenominator]];)(Fraction*)div:(Fraction*)f{return[[Fractionalloc]initWithNumerator:numerator*[fdenominator]denominator:denominator*[fnumerator]];)(Fraction*)sub:(Fraction*)f{return[[Fractionalloc]initWithNumerator:numerator*[fdenominator]-denominator*[fnumerator]denominator:denominator*[fdenominator]];}@endmain.m?import?import"Fraction.h"import"FractionMath?h”intmain(intargc,constchar*argv[]){//createanewinstance

Fraction*fracl=[[Fractionalloc]initWithNumerator:1denominator:3];. Fraction*frac2=[[Fractionalloc]initWithNumerator:2denominator:5];. Fraction*frac3=[fraclmul:frac2];//printit[fraclprint];. printf(Hn);.[frac2print];printf("=")；89. [frac3print];printf(”ヽn");//freememory.[fraclrelease];[frac2release];[frac3release];return0;}output1.1/3*2/5=2/15重點是@implementation跟@interface這兩行:?interfaceFraction(Math)以及@implementationFraction(Math).(同一個class)只能有一個同名的category?其他的categories得加上不同的、獨ー無二的名字。Categories在建立privatemethods時十分有用。因為Objective-C并沒有像Java這種private/protected/publicmethods的概念,所以必須要使用categories來達成這種功能。作法是把privatemethod從你的classheader(.h)檔案移到implementation(.m)檔案。以下是此種作法ー個簡短的範例。MyClass.h.#import..@interfaceMyClass:NSObject.-(void)publicMethod;..@endMyClass.m#import"MyClass?h”.#import. @implementationMyClass-(void)publicMethod{printf("publicmethod\n");.).@end//privatemethods@interfaceMyClass(Private)-(void)privateMethod;@end.. @implementationMyClass (Private)-(void) privateMethod{printf( "privatemethod\n");}@end.main.m#import"MyClass.h"9. intmain(intargc,constchar*argv[]){MyClass*obj=[[MyClassalloc]init];//thiscompiles.. [objpublicMethod];. //thisthrowserrorswhencompiling. //[objprivateMethod];//freememory[objrelease];return0;)output..PosingPosing有點像categories,但是不太ー樣。它允許你擴充一?個class,并且全面性地的扮演(pose)這個superclass。例如:你有一個擴充NSArray的NSArrayChiId物件。如果你讓NSArrayChild扮演NSArray,則在你的程式碼中所有的NSArray都會自動被替代為NSArrayChild。FractionB.h..#import“Fraction?h”..@interfaceFractionB:Fraction,-(void)print;.@endFractionB.m#import"FractionB.h".#import@implementationFractionB-(void)print{printf("(%i/%i)"znumeratorrdenominator);}@endmain.m#import#import"Fraction.h"

33343536373839404142434445464748495051525354555657585960616263646566676869#importMFractionB.hHintmain(intargc,constchar*argv[]){Fraction*frac=[[Fractionalloc]initWithNumerator:3denominator:10];//printitprintf("Thefractionis:”);[fracprint];printf("\n");//makeFractionBposeasFraction[FractionBposeAsClass:[Fractionclass]];Fraction*frac2=[[Fractionalloc]initWithNumerator:3denominator:10];//printitprintf("Thefractionis:");[frac2print];printf("\n");//freememory[fracrelease];[frac2release];return0;}outputfractionis:3/10

2.3.Thefractionis:(3/10)這個程式的輸出中,第一個fraction會輸出3/10,而第二個會輸出(3/10)〇這是FractionB中實作的方式。poseAsClass這個method是NSObject的一部份,它允許subclass扮演superclassoProtocolsObjective-C裡的Protocol與Java的interface或是C++的purelyvirtualclass相同。Printing.h^protocolPrinting-(void)print;@endFraction.h#import#import"Printing"@interfaceFraction:NSObject{intnumerator;intdenominator;)-(Fraction*)initWithNumerator:(int)ndenominator:(int)d;-(void)setNumerator:(int)d;-(void)setDenominator:(int)d;-(void)setNumerator:(int)nandDenominator:(int)d;-(int)numerator;-(int)denominator;@endFraction.m#import"Fraction."#import@implementationFraction-(Fraction*)initWithNumerator:(int)ndenominator:(int)d{246.self=[superinit];if(self){[selfsetNumerator:nandDenominator:d];)returnself;}-(void)print{260.printf("%i/%i",numerator,denominator);}264.-(void)setNumerator:(int)n{nnumerator=n;)-(void)setDenominator:(int)d{ddenominator=d;}276.-(void)setNumerator:(int)nandDenominator:(int)d{nnumerator=n;ddenominator=d;)-(int)denominator{returndenominator;)290.-(int)numerator{returnnumerator;)-(Fraction*)copyWithZone:(NSZone*)zone{return[[FractionallocWithZone:zone]initWithNumerator:numeratordenominator:denominator];)@endComplex.h#import#importHPrinting.hn@interfaceComplex:NSObject{doublereal;doubleimaginary;)-(Complex*)initWithReal:(double)randlmaginary:(double)i;-(void)setReal:(double)r;"(void)setImaginary:(double)i;325."(void)setReal:(double)randlmaginary: