从 C++ 到 Objective-C 的快速指南

// Objective-C

- (int) foo : (int) a : (char) b {}

+ (int) foo : (int) a : (char) b {}

// C++

intfoo(inta,charb) {}

staticintfoo(inta,charb) {}

// Objective-C

- (void) foo2 val1:(int) a;// named argument

// <span >call</span></a></span>

[obj foo2 val1:5];// merely helper: You remember that 5 is assigned to param name val1.

// Objective-C

NSObject* ptr = ...;// some pointer

[ptr foo:5:3];// <span >call</span></a></span> foo member with arguments 5 and 3

[NSObject staticfoo:5:3];// call static function of NSOBject with arguments 4 and 3

// C++

CPPObject* ptr = ...;// some pointer

ptr->foo(5,3);

CPPObject::staticfoo(5,3);

// Objective-C

@protocol foo

- (void) somefunction;

@end

@interface c1 : NSObject<foo>

@end

@implementation c1

- (void) somefunction { ... }

@end

// C++

classfoo

{

virtualvoidsomefunction() = 0;

};

classc1 :publicNSObject,publicfoo

{

voidsomefunction() { ... }

}

// Objective-C

NSObject* ptr = ...;// some pointer

[ptr somefunction:5:3];// NSObject 不必一定为其编译而实现somefunction. 如果没有被实现的话，会引发异常.

// C++

CPPObject* ptr = ...;// some pointer

ptr->somefunction(5,3);// CPPObject 必须实现 somefunction() 否则程序根本就不会被编译.

// Objective-C

NSObject* ptr = ...;// some pointer

if([ptr respondsToSelector:@selector(somefunction::)]

[ptr somefunction:5:3];

// Objective-C

NSObject* ptr = ...;// some pointer

if([ptr isKindOfClass:[fooclass]]

[ptr somefunction:5:3];

// C++

CPPObject* ptr = ...;// some pointer

foo* f =dynamic_cast<foo*>(ptr);

if(f)

f->somefunction(5,3);

// Objective-C

NSObject* ptr = ...;// some pointer

if([ptr conformsToProtocol:@protocol(foo)]

[ptr somefunction:5:3];

// C++

CPPObject* ptr = ...;// 某个也继承自foo的指针

foo* f = ptr;// 或者<span >编译器</span></a></span>会警告我们说ptr不能同foo兼容.

f->somefunction(5,3);

// Objective-C

id ptr = ...;// some pointer

if([ptr conformsToProtocol:@protocol(foo)]

[ptr somefunction:5:3];

SEL s = @selector(foo:);// a pointer to a function foo that takes 1 parameter

// C++

void* ptr = ...;// some pointer

foo* f =dynamic_cast<foo*>(ptr);

if(f)

f->somefunction(5,3);

// Objective C

@classf2;// forward declaration

@interface f1 : NSOBject// Objective-C supports only public and single inheritance

{

inttest;// default = protected

@public

inta;

intb;

f2* f;

}

- (void) foo;

@end

@implementation f1

- (void) foo

{

a = 5;// ok

self->a = 5;// ok

super.foo();// parent <span >call</span></a></span>

}

@end

// C++

classf1 :publicCPPObject

{

inttest;// default = private

public:

classf2* f;// forward declaration

inta;

intb;

voidfoo();

}

voidf1 :: foo()

{

a = 5;// ok

this->a = 5;// ok

CPPOBject::foo();// parent call

}

// Objective-C

NSObject* s = [NSObject alloc] init];// can return nil if construction failed

[s retain];// Increment the ref count

// C++

CPPObject* ptr =newCPPObject();// can throw

ptr->AddRef();

// Objective-C

NSObject* s = [NSObject alloc] initwitharg:4];

[s release];

// C++

CPPOBject* ptr =newCPPOBject(4);

ptr->Release();

// Objective C

@interface f1 : NSOBject// Objective-C supports only public and single inheritance

{

}

- (void) foo;

- (void) threadfunc :(NSInteger*) param;

- (void) mt;

@end

@implementation f1

- (void) threadfunc : (NSInteger*) param

{

[self performSelectorOnMainThread: @selector(mt)];

}

- (void) mt

{

}

- (void) foo

{

[self performSelectorInBackground: @selector(thradfunc:) withObject:1 waitUntilDone:false];

<div></div>}

@end

// Objective-C

@interface f1 : NSObject

{

}

@property (weak) NSAnotherObject* f2;// 当没有其它强引用存在的时候，它将会被自动设置成.

@end

-(void)foo

{

NSObject*s = [NSObject alloc] init];// 如果构造失败的话会返回nil

// use s

// end. Hooraah! Compiler will automati<span >call</span></a></span>y call[s release] for us!

}

// Objective-C

NSString* s1 = @"hello";

NSString* s2 = [NSString stringWithUTF8String:"A C String"];

sprintf(buff,"%s hello to %@","there",s2);

constchar* s3 = [s2 UTF8String];

// Objective-C

NSArray* a1 = [NSArray alloc] initWithObjects: @"hello",@"there",nil];

NSString* first = [a1 objectAtIndex:0];

// C++

classMyString :publicstring

{

public:

voidprintmystring() {printf("%s",c_str()); }

};

// Objective-C

@interface MyString (NSString)

- (void) printmystring;

@end

@implementation MyString (NSString)

- (void) printmystring

{

printf("%@",self);

}

@end

// C++

MyString s1 ="hi";

s1.printmystring();// ok

string s2 ="hello";

s2.printmystring();// error, we must change s2 from string to MyString

// Objective-C

NSString* s2 = @"hello";

[s2 printmystring];// valid. We extended NSString without changing types.

// Objective-C

// member function

-(void)addButtonWithTitle:(NSString*)title <span cpp string">"4_nwp"cpp string">"width: auto; height: auto; float: none;"><a cpp string">"4_nwl"href="http://cpro.baidu.com/cpro/ui/uijs.php?adclass=0&app_target="_blank"mpcpp string">"4"cpp string">"text-decoration: none;"><span cpp string">"color:#0000ff;font-size:14px;width:auto;height:auto;float:none;">block</span></a></span>:(void(^)(AlertView*, NSInteger))block;

// <span >call</span></a></span>

[object addButtonWithTitle:@"hello"block:[^(AlertView* a, NSInteger i){/*DO SOMETHING*/}];

// C++

classA

{

public:

NSObject* s;

A();

};

A :: A()

{

s = 0;// 可能会奔溃，这是常发生在发布模式下!

}

// C++

classA

{

public:

NSObject* s;

A();

};

A :: A() :s(0)// 现在编译器就知道确定 it's 是一次初始化了, 一次就不存在 [s release]

{

}

// Objective-C

NSObject* a = ...;

void* b = (__bridgevoid*)a;// 你必须在Objective-C和C类型支架使用 __bridge

void* c = (__bridge_retainedvoid*)a;// 现在是一个+1的保留计数，而你必须在稍后释放这个对象

NSObject* d = (__bridge_transfer NSObject*)c;// 现在ARC取得了对象c的”拥有权“, 将其装换成一个ARC管理的NSObject.