描述方法沒有被調用

Question

我創建了一個例子來學習objective-c中的一些基礎知識。我有一個叫Person的類，如下所示。在main方法我打電話description方法來打印一些數據，並且據我所知，description method類似於toString在java..but description方法我創建不叫

請看看下面的代碼，讓我知道爲什麼description方法的內容沒有被調用。

person.h

#import <Foundation/Foundation.h> 

@interface Person : NSObject { 
    int age; 
    int weight; 
} 

-(void) setAge:(int) age; 
-(void) setWeight: (int) weight; 

-(int) getAge; 
-(int) getWeight; 

-(NSString *) description; 

@end 

person.m

#import "Person.h" 

@implementation Person 

-(void) setAge:(int) a { 
    age = a; 
} 

-(void) setWeight:(int) w { 
    weight = w; 
} 

-(int) getAge { 
    return age; 
} 

-(int) getWeight { 
    return weight; 
} 

-(NSString *) description { 
    NSString *desc = @("my age is: %i and my weight is: %i", age, weight); 
    NSLog(@"%@", desc); 
    return desc; 
} 
@end 

主要：

#import <UIKit/UIKit.h> 
#import "AppDelegate.h" 
#import "Person.h" 

int main(int argc, char * argv[]) { 
    @autoreleasepool { 

     Person *me = [[Person alloc] init]; 

     [me setAge:20]; 
     [me setWeight:55]; 

     NSString *desc = [me description]; 
     NSLog(@"%@", desc); 

     return UIApplicationMain(argc, argv, nil, NSStringFromClass([AppDelegate class])); 
    } 
} 

Answer 1

您可能需要調用description方法，但您沒有收到日誌消息。問題出在你製作的NSString上。這是無效的：

NSString *desc = @("my age is: %i and my weight is: %i", age, weight); 

嘗試改變這一到：

NSString *desc = [NSString stringWithFormat:@"my age is: %i and my weight is: %i", age, weight];