字符串操作没有内存泄漏？ [英] String manipulation without memory leaks?

问题描述

我想做一系列字符串替换来删除xml转义的字符，例如'& amp;'。

I'd like to do a series of string substitutions to removed xml-escaped chars such as '&'.

1）有没有可以做到这一点的现有UIKit函数？

1) Is there an existing UIKit function that can do this?

2）如果没有，最好的方式做它没有泄漏记忆？这里的想法：

2) If not, what's the best way to do it without leaking memory? Here's the idea:

-(NSString*) unescape:(NSString*)string
{
    string = [string stringByReplacingOccurrencesOfString:@"'" withString:@"'"];
    string = [string stringByReplacingOccurrencesOfString:@"&" withString:@"&"];
    string = [string stringByReplacingOccurrencesOfString:@""" withString:@"\""];
    string = [string stringByReplacingOccurrencesOfString:@">" withString:@">"];
    string = [string stringByReplacingOccurrencesOfString:@"&lt;" withString:@"<"];
    return string;
}

但是不是泄漏内存与每个赋值或者stringByReplacingOccurrencesOfString返回自动释放字符串？我们如何确认stringByReplacingOccurrencesOfString字符串是自动释放？或者我们应该用 [... autorelease] / code>？

But doesn't that leak memory with each assignment? Or does stringByReplacingOccurrencesOfString return autoreleased strings? How do we confirm that stringByReplacingOccurrencesOfString strings are autoreleased? Or should we wrap them with [... autorelease]?

即使它们是自动释放的，最好避免在iPhone上自动释放（见这里）。那么我们会这样做：

Even if they are autoreleased, it's preferable to avoid autorelease on the iPhone. (See here). So then we would do:

-(NSString*) unescape:(NSString*)string
{
    NSString* string2 = [string stringByReplacingOccurrencesOfString:@"'" withString:@"'"];
    // don't release 'string' because we didn't allocate or retain it
    NSString* string3 = [string2 stringByReplacingOccurrencesOfString:@"'" withString:@"'"];
    [string2 release];
    NSString* string4 = [string3 stringByReplacingOccurrencesOfString:@"'" withString:@"'"];
    [string3 release];
    //...and so on
}     

码。写这个代码做多个替换的最好的方法是什么？

But that's pretty ugly code. What's the best way to write this code to do multiple substitutions? How would you do it?

推荐答案

任何可可方法通过不以<$ c开头的方法返回一个新对象$ c> init 或包含单词 copy 将返回一个自动释放的对象。所以上面的代码应该有noleaks。

Any cocoa method which returns a new object via a method that does not start with init or contain the word copy will return an autoreleased object. So the above code should have noleaks.

虽然这里可能更容易使用NSMutableString。然后你只是修改字符串在原地，而不是创建一堆自动释放的字符串对象，这应该使事情更清洁。

Although it may be easier to use a NSMutableString here. Then you just modify the string in place rather than creating a pile of autoreleased string objects, which should make things cleaner.

此外，如何迭代的映射字典通过，找到键，并替换为每个项目的值。也许可以保存为一个plist在您的应用程序，以便以后轻松调整。

Also, how about a dictionary of mappings that you iterate through, finding the key and replacing with the value of each item. Maybe even save this as a plist in your app for easy tweaking later.

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