这会从字符串的两端删除空格：
NSString *newString = [oldString stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];
如何从字符串的右端删除空格？
更新：来自accepted answer 的代码现在是SSToolkit 的一部分。耶！
【问题讨论】：
标签： objective-c nsstring trim strip removing-whitespace
更新：快速基准测试表明，基于Max' 和我的Matt's own adaption 表现最好。
@implementation NSString (TrimmingAdditions)
- (NSString *)stringByTrimmingLeadingCharactersInSet:(NSCharacterSet *)characterSet {
NSUInteger location = 0;
NSUInteger length = [self length];
unichar charBuffer[length];
[self getCharacters:charBuffer];
for (location; location < length; location++) {
if (![characterSet characterIsMember:charBuffer[location]]) {
break;
}
}
return [self substringWithRange:NSMakeRange(location, length - location)];
}
- (NSString *)stringByTrimmingTrailingCharactersInSet:(NSCharacterSet *)characterSet {
NSUInteger location = 0;
NSUInteger length = [self length];
unichar charBuffer[length];
[self getCharacters:charBuffer];
for (length; length > 0; length--) {
if (![characterSet characterIsMember:charBuffer[length - 1]]) {
break;
}
}
return [self substringWithRange:NSMakeRange(location, length - location)];
}
@end
然后：
NSString *trimmedString = [yourString stringByTrimmingTrailingCharactersInSet:[NSCharacterset whitespaceAndNewlineCharacterSet]];
或用于前导空格：
NSString *trimmedString = [yourString stringByTrimmingLeadingCharactersInSet:[NSCharacterset whitespaceAndNewlineCharacterSet]];
它以抽象方式实现，因此您可以将它与任何可能的NSCharacterSet、whitespaceAndNewlineCharacterSet 一起使用。
为方便起见，您可能需要添加这些包装方法：
- (NSString *)stringByTrimmingLeadingWhitespace {
return [self stringByTrimmingLeadingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]];
}
- (NSString *)stringByTrimmingTrailingWhitespace {
return [self stringByTrimmingTrailingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]];
}
- (NSString *)stringByTrimmingLeadingWhitespaceAndNewline {
return [self stringByTrimmingLeadingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];
}
- (NSString *)stringByTrimmingTrailingWhitespaceAndNewline {
return [self stringByTrimmingTrailingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];
}
编辑：使用 charBuffer 恢复到初始版本以获得更好的性能。
【讨论】：
characterAtIndex: 方法分别检索每个字符。
unichar charBuffer。不知道为什么我删除它以支持characterAtIndex:。刚刚做了一个快速基准测试，你的版本比我最初的字节缓冲版本略快。
char 缓冲区执行此操作。 1）您的代码是否处理多字节文本？ （参见Stack Overflow answer to the Most efficient way to iterate over all the chars in an NSString 的第一条评论。2）对于stringByTrimmingTrailingCharactersInSet:characterSet，不应该将length >= 0 更改为length > 0 和|| length == 0 吗？否则，charBuffer[-1] 将在length == 0 时执行。 3) 我会使用substringFromIndex 和substringToIndex，而不是substringWithRange。
length > 0 是对的。固定的。至于它是否支持多字节字符串，我不知道。需要一些测试。一些快速的基准测试显示你的代码无论如何都优于我的代码。你的不会分配额外的内存，支持多字节，实际上比我的要快一点。老实说，我实际上正在考虑删除我的答案，因为它的投票（与您的答案相比）给人的印象是最好的方法是错误的。而且我假设大多数人不阅读 cmets（好吧，无论如何都要搞砸它们，但仍然......）。你支持删除吗，马特？
基于@Regexident 和@Max 的答案，我想出了以下方法：
@implementation NSString (SSToolkitAdditions)
#pragma mark Trimming Methods
- (NSString *)stringByTrimmingLeadingCharactersInSet:(NSCharacterSet *)characterSet {
NSRange rangeOfFirstWantedCharacter = [self rangeOfCharacterFromSet:[characterSet invertedSet]];
if (rangeOfFirstWantedCharacter.location == NSNotFound) {
return @"";
}
return [self substringFromIndex:rangeOfFirstWantedCharacter.location];
}
- (NSString *)stringByTrimmingLeadingWhitespaceAndNewlineCharacters {
return [self stringByTrimmingLeadingCharactersInSet:
[NSCharacterSet whitespaceAndNewlineCharacterSet]];
}
- (NSString *)stringByTrimmingTrailingCharactersInSet:(NSCharacterSet *)characterSet {
NSRange rangeOfLastWantedCharacter = [self rangeOfCharacterFromSet:[characterSet invertedSet]
options:NSBackwardsSearch];
if (rangeOfLastWantedCharacter.location == NSNotFound) {
return @"";
}
return [self substringToIndex:rangeOfLastWantedCharacter.location+1]; // non-inclusive
}
- (NSString *)stringByTrimmingTrailingWhitespaceAndNewlineCharacters {
return [self stringByTrimmingTrailingCharactersInSet:
[NSCharacterSet whitespaceAndNewlineCharacterSet]];
}
@end
这里是 GHUnit 测试，当然都通过了：
@interface StringCategoryTest : GHTestCase
@end
@implementation StringCategoryTest
- (void)testStringByTrimmingLeadingCharactersInSet {
NSCharacterSet *letterCharSet = [NSCharacterSet letterCharacterSet];
GHAssertEqualObjects([@"zip90210zip" stringByTrimmingLeadingCharactersInSet:letterCharSet], @"90210zip", nil);
}
- (void)testStringByTrimmingLeadingWhitespaceAndNewlineCharacters {
GHAssertEqualObjects([@"" stringByTrimmingLeadingWhitespaceAndNewlineCharacters], @"", nil);
GHAssertEqualObjects([@"\n \n " stringByTrimmingLeadingWhitespaceAndNewlineCharacters], @"", nil);
GHAssertEqualObjects([@"\n hello \n" stringByTrimmingLeadingWhitespaceAndNewlineCharacters], @"hello \n", nil);
}
- (void)testStringByTrimmingTrailingCharactersInSet {
NSCharacterSet *letterCharSet = [NSCharacterSet letterCharacterSet];
GHAssertEqualObjects([@"zip90210zip" stringByTrimmingTrailingCharactersInSet:letterCharSet], @"zip90210", nil);
}
- (void)testStringByTrimmingTrailingWhitespaceAndNewlineCharacters {
GHAssertEqualObjects([@"" stringByTrimmingLeadingWhitespaceAndNewlineCharacters], @"", nil);
GHAssertEqualObjects([@"\n \n " stringByTrimmingLeadingWhitespaceAndNewlineCharacters], @"", nil);
GHAssertEqualObjects([@"\n hello \n" stringByTrimmingTrailingWhitespaceAndNewlineCharacters], @"\n hello", nil);
}
@end
我向SSToolkit 提交了一个 GitHub 拉取请求，并添加了这些方法。
【讨论】：
NSString* str = @"hdskfh dsakjfh akhf kasdhfk asdfkjash fkadshf1234 ";
NSRange rng = [str rangeOfCharacterFromSet: [NSCharacterSet characterSetWithCharactersInString: [str stringByReplacingOccurrencesOfString: @" " withString: @""]] options: NSBackwardsSearch];
str = [str substringToIndex: rng.location+1];
【讨论】：
需要稍作改动以解决最后一个非尾随字符为多字节的情况：
- (NSString *)stringByTrimmingTrailingCharactersInSet:(NSCharacterSet *)characterSet {
NSRange rangeOfLastWantedCharacter = [self rangeOfCharacterFromSet:[characterSet invertedSet]
options:NSBackwardsSearch];
if (rangeOfLastWantedCharacter.location == NSNotFound) {
return @"";
}
return [self substringToIndex:rangeOfLastWantedCharacter.location + rangeOfLastWantedCharacter.length]; // non-inclusive
}
【讨论】：