Objective-C語法小總結

1，方法調用

    （1）調用對象的方法：

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

    （2）調用類的方法：（創建對象）

id myObject = [NSString string]; 

或

NSString* myString = [NSString string]; 

    （3）嵌套調用：

[NSString stringWithFormat:[prefs format]];

    （4）多輸入參數：

聲明：

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

調用：

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

2.訪問器

    （1）setter

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

    （2）點操作符

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

3.創建對象

    （1）創建自動釋放的對象

NSString* myString = [NSString string];

    （2）手工alloc創建

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

    注：[NSString alloc] 是NSString類本身的alloc方法調用。這是一個相對低層的調用，它的作用是分配內存及實例化一個對象。

            [[NSString alloc] init] 調用新創建對象的init方法。init方法通常做對象的初始化設置工作，比如創建實例變量。

4.內存管理

//string1 將被自動釋放 
NSString* string1 = [NSString string]; 
 
//必須在用完後手工釋放 
NSString* string2 = [[NSString alloc] init]; 
[string2 release]; 

5.類接口

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.類實現

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.日誌記錄: NSLog()

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

8.屬性(Property)

用屬性改寫後的接口：

#import <Cocoa/Cocoa.h> 
 
@interface Photo : NSObject { 
    NSString* caption; 
    NSString* photographer; 
} 
@property (retain) NSString* caption; 
@property (retain) NSString* photographer; 
 
@end 

改寫後的實現部分：

#import "Photo.h" 
         
@implementation Photo 
 
@synthesize caption; 
@synthesize photographer; 
 
- (void) dealloc 
{ 
    self.caption = nil; 
    self.photographer = nil;
    [super dealloc]; 
} 
 
@end

9.類目(Category)

聲明：

#import <Cocoa/Cocoa.h> 
             
@interface NSString (Utilities) 
- (BOOL) isURL; 
@end 

實現：

#import "NSString-Utilities.h" 
             
@implementation NSString (Utilities) 
 
- (BOOL) isURL 
{ 
    if ( [self hasPrefix:@"http://"] ) 
        return YES; 
    else 
        return NO; 
} 
 
@end