NSString 分割
An NSString object represents a string of ordered characters (text). An NSCharacterSet object represents a set of characters in no particular order. It is often much quicker to determine whether a character is a member of an NSCharacterSet than an NSString. You can't use an NSCharacterSet object to hold text, at least not in any sensible way, because it does not maintain any order of characters, its use is primarily for determining whether a character exists in a set of characters.
我们在nsstring的分割，查找等操作中，经常会提供两种函数，参数类型分别为NSString 和NSCharacterset，有什么不同呢？
NSString 是有序字符串
NSCharacterset是无需字符集合，主要用来判断已知字符串是否包含制定字符集，而不可以用来保存字符串。
转自：
在ios中 可以使用stringByTrimmingCharactersInSet函数过滤字符串中的特殊符号
首先自己定义一个NSCharacterSet, 包含需要去除的特殊符号
NSCharacterSet *set = [NSCharacterSetcharacterSetWithCharactersInString:@"@／：；（）￥「」＂、[]{}#%-*+=_\\|~＜＞$€^·'@#$%^&*()_+'""];
由于NSString中有全角符号和半角符号, 因此有些符号要包括全角和半角的
然后调用stringByTrimmingCharactersInSet
NSString *trimmedString = [stringstringByTrimmingCharactersInSet:set];
trimmedString就是过滤后的字符串
转自：
NSCharacterSet 去除NSString中的空格
去除 username中的空格，tablenewline，nextline
代码如下：NSCharacterSet *whitespace =[NSCharacterSet whitespaceAndNewlineCharacterSet]; NSString * username =[mUsernameField stringValue]; username =[username stringByTrimmingCharactersInSet:whitespace]; 注释：stringByTrimmingCharactersInSet: Returns a new string made by removing from both ends of the receiver characters contained in a given characterset. whitespaceAndNewlineCharacterSet Returns a character set containing only the whitespace charactersspace (U+0020) and tab (U+0009) and the newline and nextlinecharacters (U+000A–U+000D, U+0085). 另外可以用 whitespaceCharacterSet 替换 whitespaceAndNewlineCharacterSet 区别newlinenextline whitespaceCharacterSet Returns a character set containing only the in-line whitespacecharacters space (U+0020) and tab (U+0009).
NSString *temptext =[messageTextField.texts tringByTrimmingCharactersInSet:[NSCharacterSetwhitespaceCharacterSet]];
NSString *text = [temptextstringByTrimmingCharactersInSet:[NSCharacterSetwhitespaceAndNewlineCharacterSet ]];第1行是去除2端的空格
第2行是去除回车
转自：
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。
@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。
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：
[@"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。