NSString处理－会陆续更新

1.用正则表达式截取 字符串中的数字。
代码如下

1.过滤掉不是数字的字符串

//过滤掉不是数字的字符串
NSString *myPhoneNumber = @" 12 34678a9 ";
    NSLog(@"%zd",myPhoneNumber.length); //输出：12
    myPhoneNumber =  [myPhoneNumber stringByReplacingOccurrencesOfString:@"[^0-9]" withString:@"" options:NSRegularExpressionSearch range:NSMakeRange(0, [myPhoneNumber length])];
    NSLog(@"%zd",myPhoneNumber.length); //输出：8
    NSLog(@"%@",myPhoneNumber); //输出：12346789

2. 去除空格

//1  去除字符串前后的空格
[string stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]]

//2 去除字符串所有的空格
[string stringByReplacingOccurrencesOfString:@" " withString:@""]

3. 判断字符串是否为空

+ (BOOL) isEmpty: (NSString *)string {
    if (string == nil || string == NULL) {
        return YES;
    }
    if ([string isKindOfClass:[NSNull class]]) {
        return YES;
    }
    if ([[string stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]] length]==0) {
        return YES;
    }
    return NO;
}