Cocoa - 修剪来自NSString的所有领先的空格 [英] Cocoa - Trim all leading whitespace from NSString

问题描述

（已搜索，但无法在此找到一个简单的解决方案，或在Cocoa文档中找到）

(have searched, but not been able to find a simple solution to this one either here, or in Cocoa docs)

Q。如何仅从NSString修剪所有领先的空格？

Q. How can I trim all leading whitespace only from an NSString? (i.e. leaving any other whitespace intact.)

不幸的是，为了我的目的，NSString的stringByTrimmingCharactersInSet方法可以在前导和尾随。

Unfortunately, for my purposes, NSString's stringByTrimmingCharactersInSet method works on both leading and trailing.

需要Mac OS X 10.4兼容性，手动GC。

Mac OS X 10.4 compatibility needed, manual GC.

推荐答案

这将创建一个NSString类别， 。这样，你可以调用 NSString * newString = [mystring stringByTrimmingLeadingWhitespace]; 获得一个副本减去前导空格。 （代码未经测试，可能需要一些小调试。）

This creates an NSString category to do what you need. With this, you can call NSString *newString = [mystring stringByTrimmingLeadingWhitespace]; to get a copy minus leading whitespace. (Code is untested, may require some minor debugging.)

@interface NSString (trimLeadingWhitespace)
-(NSString*)stringByTrimmingLeadingWhitespace;
@end

@implementation NSString (trimLeadingWhitespace)
-(NSString*)stringByTrimmingLeadingWhitespace {
    NSInteger i = 0;

    while ((i < [self length])
           && [[NSCharacterSet whitespaceCharacterSet] characterIsMember:[self characterAtIndex:i]]) {
        i++;
    }
    return [self substringFromIndex:i];
}
@end

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