去空格 whitespaceAndNewlineCharacterSet和过滤字符串

一、过滤字符串

　　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 = [NSCharacterSet characterSetWithCharactersInString:@"@／：；（）¥「」＂、[]{}#%-*+=_//|~＜＞$€^•'@#$%^&*()_+'/"""];

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 = [string stringByTrimmingCharactersInSet:set];

trimmedString就是过滤后的字符串

二、去除空格

　　1.去掉两端的空格

[str stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]]

　　2.去掉多余的空格

 NSString *str = @"    this     is a    test    .   ";  

     NSCharacterSet *whitespaces = [NSCharacterSet whitespaceCharacterSet];
     NSPredicate *noEmptyStrings = [NSPredicate predicateWithFormat:@"SELF != ''"];  

     NSArray *parts = [str componentsSeparatedByCharactersInSet:whitespaces];
     NSArray *filteredArray = [parts filteredArrayUsingPredicate:noEmptyStrings];
     str = [filteredArray componentsJoinedByString:@" "]; 

　　3.去掉所有空格

[str stringByReplacingOccurrencesOfString:@" " withString:@""]

　　4.去掉最左边的空格  和  去掉最右边的空格

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

@implementation NSString (TrimmingAdditions)  

- (NSString *)stringByTrimmingLeftCharactersInSet:(NSCharacterSet *)characterSet {
    NSUInteger location = ;
    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 = ;
    NSUInteger length = [self length];
    unichar charBuffer[length];
    [self getCharacters:charBuffer];  

    for (length; length > ; length--) {
        if (![characterSet characterIsMember:charBuffer[length - ]]) {
            break;
        }
    }  

    return [self substringWithRange:NSMakeRange(location, length - location)];
}  

@end  

例如：NSLog(@"%@",[@"abc 123 " stringByTrimmingRightCharactersInSet:[NSCharacterSet whitespaceCharacterSet]]);

　　：NSLog(@"%@",[@"0.012300" stringByTrimmingRightCharactersInSet:[NSCharacterSet characterSetWithCharactersInString:@"0"]])；

一个非常好的例子,来源于http://nshipster.com/nscharacterset/, 去掉多余的空格(包括两端的和中间的)

NSString *exampleStr = @" My name    is Johnny!";
exampleStr = [exampleStr stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]];
NSArray *exampleArr = [exampleStr componentsSeparatedByCharactersInSet:[NSCharacterSet whitespaceCharacterSet]];
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"self <> ''"];
exampleArr = [exampleArr filteredArrayUsingPredicate:predicate];
exampleStr = [exampleArr componentsJoinedByString:@" "];