從另一個文件調用方法

Question

我是Objective-C的初學者。我想從文件me.m中調用文件you.m中的方法two。你能教我用下面的簡單例子來理解。謝謝！

you.h

#import <Foundation/Foundation.h> 
@interface you : NSObject { 
} 
- (NSString *)one; 
- (NSString *)two; 
@end 

you.m

#import "you.m" 

@implementation you 
- (NSString *)one { 
    NSString *a = @"this is a test."; 
    return a; 
} 
-(NSString *)two { 
    NSString *b = [self one]; 
    return b; 
} 
@end 

me.h

#import <Foundation/Foundation.h> 
@interface me : NSObject { 
} 
@end 

me.m

#import "you.h" 
#import "me.h" 

@implementation me 
-(void)awakeFromNib{ 
    //NSString *obj = [[[NSString alloc] init] autorelease]; 
    //NSString *str = [obj two]; // dont work 
    //NSString *str = [self two]; // dont work 
    // I'd like to call method *two* from here. 
    NSLog(@"%@", str); 
} 
@end 

Answer 1

在me類，建立you一個實例。

you *objectYou=[you new]; 

由於two返回一個字符串，你需要將它存儲：

NSString *string=[objectYou two]; 

在您的代碼：

-(void)awakeFromNib{ 
    you *objectYou=[you new]; 
    NSString *str = [objectYou two]; 
    NSLog(@"%@", str); 
} 

注：按照命名規則。類名必須以大寫字母開頭，如Me，您。

編輯：

當你正在學習，我想補充一點，因爲你是從調用twoone。如果one不意味着被稱爲you類之外。您可以在.m中定義它，並從.h中刪除聲明。

Answer 2

很簡單，在Me類中創建一個You類的實例並調用該成員函數。像這樣 -

you *youInstance = [[you alloc] init]; 
NSString *retStr = [youInstance two]; 

順便說一句，它是一個很好的做法，CamelCase類名。

還要注意這一點 -

@interface you 
- (NSString *) twoInstanceMethod; 
+ (NSString *) twoClassMethod; 
@end 

NSString *retStr = [you twoClassMethod]; // This is ok 

NSString *retStr = [you twoInstanceMethod]; // this doenst't work, you need an instance: 

//so we create instance. 
you *youInstance = [[you alloc] init]; 
NSString *retStr = [youInstance two]; 

希望這將清除一些概念...