NSMutableString stringByReplacingOccurrencesOfString警告 [英] NSMutableString stringByReplacingOccurrencesOfString Warning

问题描述

我有一个RSS解析器方法，我需要从我提取的html摘要中删除空格和其他废话。我有一个NSMutableString类型'currentSummary'。当我打电话时：

I've got an RSS parser method and I need to remove whitespace and other nonsense from my extracted html summary. I've got a NSMutableString type 'currentSummary'. When I call:

currentSummary = [currentSummary 
        stringByReplacingOccurrencesOfString:@"\n" withString:@""];

Xcode告诉我警告：从不同的Objective-C类型分配

Xcode tells me "warning: assignment from distinct Objective-C type"

这有什么问题？

推荐答案

如果 currentSummary 已经是一个NSMutableString你不应该尝试为它分配一个常规的NSString（ stringByReplacingOccurrencesOfString：withString：的结果）。

If currentSummary is already a NSMutableString you shouldn't attempt to assign a regular NSString (the result of stringByReplacingOccurrencesOfString:withString:) to it.

而是使用可变等效 replaceOccurrencesOfString：withString：options：range：，或者添加对 mutableCopy的调用：

Instead use the mutable equivalent replaceOccurrencesOfString:withString:options:range:, or add a call to mutableCopy before the assignment:

// Either
[currentSummary replaceOccurencesOfString:@"\n" 
                               withString:@"" 
                                  options:NULL
                                    range:NSMakeRange(0, [receiver length])];

// Or
currentSummary = [[currentSummary stringByReplacingOccurrencesOfString:@"\n"
                                                            withString:@""]
                  mutableCopy];

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