objective-c - Objective-C 中的嵌套数组 (NSMutableArray)

Question

我正在尝试构建一个嵌套数组:首先，我制作了一个包含 10 个数组的“PlayerItems”数组，每个数组包含项目对象，对应于游戏中每个玩家的库存。在指示的行上，我收到以下错误:

error: void valued not ignored as it ought to be

这里的void值是多少？如果我改用 [[PlayerItems objectAtIndex:i] addObject:myitem]，程序会编译但会崩溃。如果我注释掉该行，它会编译并运行正常。感谢您的帮助!

self.PlayerItems = [[NSMutableArray alloc] initWithCapacity:11];
NSMutableArray *itemarray = [[NSMutableArray alloc] initWithCapacity:60];
item *myitem = [[item alloc] init];
item.kind = 1;
for (int i = 1; i < 10; i++) {
    itemarray = [[NSMutableArray alloc] initWithCapacity:60];
    [PlayerItems addObject:itemarray];
    for (int i2 = 1; i2 < 50; i2++) {
        myitem = [[item alloc] init];
        myitem.kind = 1;
        // The error occurs on the line below:
        ((NSMutableArray *) [[PlayerItems objectAtIndex:i] addObject:myitem]);
    }
}

Answer 1

我会这样做:

self.playerItems = [[NSMutableArray alloc] initWithCapacity:11];

NSMutableArray * itemArray;
Item * anItem;
for (int playerIndex = 1; playerIndex <= 10; playerIndex++)
{
    itemArray = [NSMutableArray arrayWithCapacity:60];
    [playerItems addObject:itemArray];

    for (int itemIndex = 1; itemIndex <= 50; itemIndex++)
    {
        anItem = [[Item alloc] init];
        anItem.kind = 1;
        [itemArray addObject:anItem];
        [anItem release];
    }
}

作为旁注，您绝对应该阅读 memory management in Cocoa ，因为您的原始代码充满了内存泄漏。一开始可能有点难以理解，但一旦你学会了，它就会成为第二天性。非常值得付出努力。

更新:

一个更面向对象的方法是创建一个 Player 类，并让每个 Player 管理自己的项目集:

Player.h

@interface Player : NSObject
{
    NSMutableArray * items;
}
@property (readonly) NSMutableArray * items;
@end

Player.m

#import "Player.h"
@implementation Player

@synthesize items;

- (id)init
{
    if ((self = [super init]) == nil) { return nil; }

    items = [[NSMutableArray alloc] initWithCapacity:60];
    Item * anItem;
    for (int itemIndex = 1; itemIndex <= 50; itemIndex++)
    {
        anItem = [[Item alloc] init];
        anItem.kind = 1;
        [items addObject:anItem];
        [anItem release];
    }

    return self;
}

- (void)dealloc
{
    [items release];
    [super dealloc];
}

@end

别处

NSMutableArray * allPlayers = [[NSMutableArray alloc] initWithCapacity:11];

Player * aPlayer;
for (int playerIndex = 1; playerIndex <= 10; playerIndex++)
{
    aPlayer = [[Player alloc] init];
    [allPlayers addObject:aPlayer];
    [aPlayer release];
}

...

[allPlayers release];