去空格 whitespaceAndNewlineCharacterSet

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:@""]