NSMutableArray 总是空的? [英] NSMutableArray always empty?

问题描述

理解Obj-C的记忆和一些概念还是有些困难.

Still have some difficulties to understand Obj-C's gestion of memory and some of its concepts.

所以我的主类包含一个 NSMutableArray 包含一些字符和他们的武器列表.是这样的:

So my main class contains a NSMutableArray containing some characters and their list of weapons. It's like this :

在主类.h

@property (nonatomic, retain) NSMutableArray *players;

在 Main class.m 的 init

for(int i = 0 ; i < 30 ; i++)
{
    [players addObject:[[PlayerInGame alloc] init:[self.tabPlayers objectAtIndex:i] :[self.tabWeapons:objectAtIndex:i]]];
}

PlayerInGame.h

@property (nonatomic, retain) NSMutableArray *weaponsList;

PlayerInGame.m

- (id) init : (Player*) player : (Weapon*) weapon
{
    [self.weaponsList addObject:weapon];
    // Then I try NSLog of weaponsList's count.
}

这里的武器列表总是空的.怎么了?

Here weaponsList is always empty. What is wrong?

推荐答案

其他答案是对的.在任何其他语言上，如果您引用未分配的对象，您将获得 NullPointerException.但是在目标 C 中，发送到 nil 的方法只返回 0，它不会使应用程序崩溃.如果您想进一步阅读，请阅读 this

The other answers are right. On any other language if you reference a unallocated object you will get a NullPointerException. But in objective C the method sent to nil just returns 0 and it won't crash the app.. If you want further read, read this

这就是为什么

[self.weaponsList addObject:weapon];

没有崩溃，而在 java 中，如果您尝试将对象添加到未分配的数组中，您的程序将崩溃.. 正如其他答案所指出的，声明

didn't crash, while in java if you try to add object to a unallocated array your program will crash.. As other answers pointed out, the statement

self.weaponsList = [[[NSMutableArray alloc] init] autorelease];

分配内存来存储数组，并且引用返回给变量weatherList.现在武器列表 != nil.

alloc memory to store array, and a reference is given back to to variable weaponList. Now weaponList != nil.

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