字符串替换

    NSString *str = @"http:**520it.com*img*ljn.gif";
    NSString *newStr = [str stringByReplacingOccurrencesOfString:@"*" withString:@"/"];
    NSLog(@"newStr = %@", newStr);

输出结果: http://www.520it.com/img/ljn.gif

    NSString *str =  @"   http://520it.com/img/ljn.gif   ";
    NSString *newStr = [str stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]];
    NSLog(@"str =|%@|", str);
    NSLog(@"newStr =|%@|", newStr);

输出结果:
str =|   http://520it.com/img/ljn.gif   |
newStr =|http://520it.com/img/ljn.gif|

    NSString *str =  @"***http://520it.com/img/ljn.gif***";
    NSString *newStr = [str stringByTrimmingCharactersInSet:[NSCharacterSet characterSetWithCharactersInString:@"*"]];

    NSLog(@"str =|%@|", str);
    NSLog(@"newStr =|%@|", newStr);

输出结果:
str =|***http://520it.com/img/ljn.gif***|
newStr =|http://520it.com/img/ljn.gif|