如何去掉String的前后空格或某字符

Question

如题所述

Answer 1

在objective-c中，如何去掉一个string的前后的空格字符或某个特定字符呢？
如@“ abc 123 ”字符串前后有空格，该如何去掉？
使用nsstring的实例方法stringByTrimmingCharactersInSet：可以解决该问题。
方法如下：
C代码
[@" abc 123 " stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]]；

NSString *newString = [oldString stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];

NSString中该方法说明如下：
stringByTrimmingCharactersInSet:
Returns a new string made by removing from both endsof the receiver characters contained in a given character set.
- (NSString *)stringByTrimmingCharactersInSet:(NSCharacterSet*)set
Parameters
set
A character set containing the characters to removefrom the receiver. set must not be nil.
Return Value
A new string made by removing from both ends of thereceiver characters contained in set. If the receiver is composedentirely of characters from set, the empty string is returned.

(miki西游 @mikixiyou 原文链接: http://mikixiyou.iteye.com/blog/1623323)

这是典型的其他语言中trim方法。我要问的是，如何去掉最左边的空格？又该如何去掉最右边的空格？
在NSString的类中没有提供实现这类需求的方法，我们只能手工去添加这些方法。

C代码
@interface NSString (TrimmingAdditions)
- (NSString *)stringByTrimmingLeftCharactersInSet:(NSCharacterSet *)characterSet ;
- (NSString *)stringByTrimmingRightCharactersInSet:(NSCharacterSet *)characterSet ;
@end

@implementation NSString (TrimmingAdditions)

- (NSString *)stringByTrimmingLeftCharactersInSet:(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 *)stringByTrimmingRightCharactersInSet:(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

使用stringByTrimmingRightCharactersInSet方法去掉一个字符串最右边的空格。
C代码
NSLog(@"%@",[@"abc 123 " stringByTrimmingRightCharactersInSet:[NSCharacterSet whitespaceCharacterSet]]);

如何去掉一个字符串@“0.012300”最右边的“0“呢？这是典型的float格式化成字符串以后的形式，显示时最好去掉最右边的“0”。
解决方法如下：
C代码
[@"0.012300" stringByTrimmingRightCharactersInSet:[NSCharacterSet characterSetWithCharactersInString:@"0"]]；

在NSString中trim字符时，不理解为何不提供分别去掉左右字符的方法，如其他语言的ltrim和rtim。