Objective-C和@Interface文件中的數組

Question

我剛開始學習Objective-C，並試圖理解下面的代碼。有3個文件：FindLargestNumber.h，FindLargestNumber.m和main.m.

在FindLargestNumber.h文件中，我想知道是否有人能解釋我@interface NSMutableArray (FindLargestNumber)的含義。我期待看到像@interface FindLargestNumber: NSObject那樣的東西。

#import <Foundation/Foundation.h> 

@interface NSMutableArray (FindLargestNumber) 

- (id)largest:(NSMutableArray *)array; 

@end 

------------------------------------------------------------ 

#import "FindLargestNumber.h" 

@implementation NSMutableArray (FindLargestNumber) 

- (id)largest:(NSMutableArray *)array { 
    id currentLargest = @0; 
    for (id item in array) { 
     if (item > currentLargest) { 
      currentLargest = item; 
     } 
    } 
    return currentLargest; 
} 

@end 

------------------------------------------------------ 

#import <Foundation/Foundation.h> 
#import "FindLargestNumber.h" 

int main(int argc, const char * argv[]) { 
    @autoreleasepool { 
     NSMutableArray *array = [NSMutableArray arrayWithObjects: @1, @4, @743, @77, @0, nil]; 
     //NSLog(@"%@", array); 
     NSLog(@"The largest value is %@", [array largest:array]); 
    } 
    return 0; 
} 

Answer 1

NSMutableArray類（已存在）正在通過添加名爲largest:的新方法進行擴展。在Objective-C中，類使用類別進行擴展，這裏的類別名爲FindLargestNumber。詳情請參閱https://developer.apple.com/library/content/documentation/General/Conceptual/DevPedia-CocoaCore/Category.html。