Objective-C语法小总结

1，方法调用

（1）调用对象的方法：

output = [object methodWithOutput];
output = [object methodWithInputAndOutput:input];

（2）调用类的方法：（创建对象）

id myObject = [NSString string];

或

NSString* myString = [NSString string];

（3）嵌套调用：

[NSString stringWithFormat:[prefs format]];

（4）多输入参数：

声明：

-(BOOL)writeToFile:(NSString *)path atomically:(BOOL)useAuxiliaryFile;

调用：

BOOL result = [myData writeToFile:@"/tmp/log.txt" atomically:NO];

2.访问器

（1）setter

[photo setCation:@”Day at the Beach”];
output = [photo caption];

（2）点操作符

photo.caption = @”Day at the Beach”;
output = photo.caption;

3.创建对象

（1）创建自动释放的对象

NSString* myString = [NSString string];

（2）手工alloc创建

NSString* myString = [[NSString alloc] init];

注：[NSString alloc] 是NSString类本身的alloc方法调用。这是一个相对低层的调用，它的作用是分配内存及实例化一个对象。

[[NSString alloc] init] 调用新创建对象的init方法。init方法通常做对象的初始化设置工作，比如创建实例变量。

4.内存管理

//string1 将被自动释放
NSString* string1 = [NSString string];

//必须在用完后手工释放
NSString* string2 = [[NSString alloc] init];
[string2 release];

5.类接口

Photo.h

#import <Cocoa/Cocoa.h>

@interface Photo : NSObject {
NSString* caption;
NSString* photographer;
}

- (NSString*)caption;
- (NSString*)photographer;

- (void) setCaption: (NSString*)input;
- (void) setPhotographer: (NSString*)input;

6.类实现

Photo.m

#import "Photo.h"

@implementation Photo

- (NSString*) caption {
return caption;
}

- (NSString*) photographer {
return photographer;
}

- (void) setCaption: (NSString*)input
{
[caption autorelease];
caption = [input retain];
}

- (void) setPhotographer: (NSString*)input
{
[photographer autorelease];
photographer = [input retain];
}
- (void) dealloc
{
[caption release];
[photographer release];
[super dealloc];
}
@end

7.日志记录: NSLog()

NSLog ( @"The current date and time is: %@", [NSDate date] );

8.属性(Property)

用属性改写后的接口：

#import <Cocoa/Cocoa.h>

@interface Photo : NSObject {
NSString* caption;
NSString* photographer;
}
@property (retain) NSString* caption;
@property (retain) NSString* photographer;

@end

改写后的实现部分：

#import "Photo.h"

@implementation Photo

@synthesize caption;
@synthesize photographer;

- (void) dealloc
{
self.caption = nil;
self.photographer = nil;
[super dealloc];
}

@end

9.类目(Category)

声明：

#import <Cocoa/Cocoa.h>

@interface NSString (Utilities)
- (BOOL) isURL;
@end

实现：

#import "NSString-Utilities.h"

@implementation NSString (Utilities)

- (BOOL) isURL
{
if ( [self hasPrefix:@"http://"] )
return YES;
else
return NO;
}

@end