類型數組的問題

Question

嘿傢伙我試圖建立一個數據庫，將NSStrings映射到int。我有叫Movie.h類，每個對象都有一個名稱，並分配了一個數字：

//Movie.h 
@interface Movie : NSObject 
{ 
    int m_num; 
    NSString *m_name; 
} 
@property int m_num; 
@property(nonatomic, retain) NSString *m_name; 
@end 

//Movie.m 
@implementation Movie 
@synthesize m_num, m_name; 
@end 

然後我有另一個類調用地圖，我實現的功能與我的「電影」玩。其中一個函數稱爲insert，它將類電影的對象插入到應該存儲所有電影的數組中。代碼編譯，但我的「m_array」似乎沒有記錄我添加到它的內容。下面是代碼：

//Map.h 
#import "Movie.h" 
@interface Map : NSObject 
{ 
@private 
    int m_count; 
    NSMutableArray *m_array; 
} 
@property int m_count; 
@property(nonatomic, retain) NSMutableArray *m_array; 
-(bool) contain: (NSString *) name; 
-(bool) insert: (NSString *) name: (int) chap; 
@end 

//Map.m 
@implementation Map 
@synthesize m_count, m_array; 

//Constructor 
-(id) init{ 
    if (self = [super init]){ 
     m_count = 0; 
    } 
    return self; 
} 
-(bool) contain: (NSString *) name{ 
    bool b = false; 
    for (int i = 0; i < m_count; i++) { 
     Movie *m = [[Movie alloc]init]; 
     m = [m_array objectAtIndex:i]; 
     NSLog(@"%@ came out in %i", m.m_name, m.m_num); 
     if (m.m_name == name) { 
      b = true; 
     } 
    } 
    return b; 
} 
-(bool) insert:(NSString *) name: (int) chap{ 
    Movie *m1 = [[Movie alloc]init]; 
    m1.m_name = name; 
    m1.m_num = chap; 
    [m_array addObject:m1]; 
    NSLog(@"Here is the object %@",[m_array objectAtIndex:m_count]); 
    m_count++; 
    return true; 
} 
@end 

-(bool) upgrade:(NSString *)name :(int)chap{ 
    if(![self contain:name]) 
     return false; 
    for (int i = 0; i < m_count; i++){ 
     Movie *m = [[Movie alloc]init]; 
     m = [m_array objectAtIndex:i]; 
     if(m.m_name == name) 
      m.m_num = chap; 
    } 
    return true; 

}

這裏是我的主：

//main.m 
#import "Map.h" 

int main (int argc, const char * argv[]) 
{ 
    @autoreleasepool 
    { 
     Map *m = [[Map alloc]init]; 
     [m insert:@"James Bond" :2001]; 
     if (![m contain:@"James Bond"]) { 
      NSLog(@"It does not work"); 
     } 
    } 
    return 0; 
} 

這裏是控制檯輸出：

2012-02-27 14:20:04.923 myMap[3926:707] Here is the object (null) 
2012-02-27 14:20:05.036 myMap[3926:707] (null) came out in 0 
2012-02-27 14:20:05.037 myMap[3926:707] It does not work 

Answer 1

看起來你忘了創建數組：

- (id)init 
{ 
    self = [super init] 
    if (nil != self) { 
    m_count = 0; 
    m_array = [NSMutableArray new]; << here 
    } 
    return self; 
} 

沒有創建它，它只是nil。