objective-c 如何清除字典？
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How to clear a dictionary?
提问by 4thSpace
I'm currently doing the following to clear out an NSMutableDictionary
我目前正在执行以下操作以清除 NSMutableDictionary
[myDictionary release];
myDictionary = [[NSMutableDictionary alloc] init];
The release line doesn't actually release any objects in the dictionary. I can still see all of them on the next line. It isn't until the alloc line is executed that the dictionary is zeroed out. Is there a better way to do it?
释放行实际上并没有释放字典中的任何对象。我仍然可以在下一行看到所有这些。直到执行 alloc 行，字典才被清零。有没有更好的方法来做到这一点？
回答by Andy White
I can't test it at the moment, but have you tried the removeAllObjectsmethod of NSMutableDictionary?
我暂时无法测试，但是您尝试过 的removeAllObjects方法NSMutableDictionary吗？
回答by bbum
You say:
你说：
The release line doesn't actually release any objects in the dictionary. I can still see all of them on the next line. It isn't until the alloc line is executed that the dictionary is zeroed out. Is there a better way to do it?
释放行实际上并没有释放字典中的任何对象。我仍然可以在下一行看到所有这些。直到执行 alloc 行，字典才被清零。有没有更好的方法来做到这一点？
If -releaseof the mutable dictionary causes the dictionary to be deallocated -- drops the retain count to zero -- then the mutable dictionary will release all contained objects. Always.
如果-release可变字典的 导致字典被释放——将保留计数降至零——那么可变字典将释放所有包含的对象。总是。
Thus, if the objects aren't being released, then this suggested "fix"...
因此，如果对象没有被释放，那么这个建议的“修复”......
[myDictionary removeAllObjects];
[myDictionary release];
myDictionary = [[NSMutableDictionary alloc] init];
... is a memory leak in that the original instance of NSMutableDictionary will be leaked.
... 是内存泄漏，因为 NSMutableDictionary 的原始实例将被泄漏。
As a result, calling -removeAllObjectswillempty the dictionary and release all of the contained objects, but you still have a memory leak that you should figure out and fix.
因此，调用-removeAllObjects将清空字典并释放所有包含的对象，但您仍然存在内存泄漏，您应该找出并修复它。
To be blunt:
坦率地说：
If the objects in your dictionary are not being deallocated when the dictionary receives the above -release(without calling -removeAllObjects), then there is a memory leak. It is either:
如果在字典接收到上述内容时-release（没有调用-removeAllObjects），字典中的对象没有被释放，则存在内存泄漏。它是：
The objects in the dictionary have been retained an extra time.
There is still an outstanding
-retainon the dictionary.
字典中的对象被保留了额外的时间。
-retain字典上还有一个突出 的。
Since you say the objects are being correctly (as in, as expected) deallocated when you call -removeAllObjects, then it must be (2). Look through your code and figure out where there is an extra -retainof the dictionary. You can use the Object Allocinstrument to figure out exactly where all of the retains come from.
既然您说对象在调用 时被正确（如预期的那样）释放-removeAllObjects，那么它必须是（2）。查看您的代码并找出-retain字典的额外内容。您可以使用Object Alloc工具来确定所有保留的确切来源。
回答by Ben Gottlieb
-removeAllObjects will work, as Andy mentioned. However, if any of your dictionary's objects are auto-released, or if the dictionary itself has been autoreleased somewhere along the line, then they won't be dealloc'd until the next time the runloop finishes (when the autorelease pool is drained).
-removeAllObjects 将起作用，正如安迪提到的那样。但是，如果您的字典中的任何对象是自动释放的，或者字典本身已在该行的某处自动释放，那么在下一次运行循环完成之前（当自动释放池耗尽时）它们不会被释放.
回答by Dan
[aMutableDictionary removeAllObjects];
from Apple's documentation:
来自苹果的文档：
(void)removeAllObjectsDescription - Empties the dictionary of its entries. Each key and corresponding value object is sent a release message.
Availability - iOS (2.0 and later)
(void)removeAllObjects描述 - 清空其条目的字典。每个键和相应的值对象都会发送一条释放消息。
可用性 - iOS（2.0 及更高版本）
