Cocoa - 从 NSString 中修剪所有前导空格 [英] Cocoa - Trim all leading whitespace from NSString

问题描述

(已经搜索过，但无法在此处或 Cocoa 文档中找到简单的解决方案)

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

问.如何仅从 NSString 中修剪所有 前导 空格?(即保留任何其他空白不变.)

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

不幸的是，就我而言，NSString 的 stringByTrimmingCharactersInSet 方法对前导和尾随都有效.

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

需要兼容 Mac OS X 10.4，手动 GC.

Mac OS X 10.4 compatibility needed, manual GC.

推荐答案

这将创建一个 NSString 类别来执行您需要的操作.有了这个，你可以调用 NSString *newString = [mystring stringByTrimmingLeadingWhitespace]; 来获得一个减去前导空格的副本.(代码未经测试，可能需要一些小的调试.)

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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