iOS 补零

+ (NSString*)sha_amount:(NSString *)amount{

    NSScanner *scan = [NSScanner scannerWithString:amount];

    int val; // 先判断整数和小数；整数直接补.0000;小数的话不够的话补0;超过的话截取

    if([scan scanInt:&val] && [scan isAtEnd]){ // 是整数

        amount = [NSString stringWithFormat:@"%@%@",scan.string,@".0000"];

    }else{

        if([scan.string rangeOfString:@"."].location !=NSNotFound){

            NSArray *scanArray = [scan.string componentsSeparatedByString:@"."]; //字符串按照;分隔成数

            NSString *scanLast = [scanArray lastObject];

            if(scanLast.length < 4){

                float floatString = [scan.string floatValue];

                amount = [NSString stringWithFormat:@"%.4f",floatString];

            }else{

                amount = [NSString stringWithFormat:@"%@%@%@",[scanArray firstObject],@".",[scanLast substringToIndex:4]];

            }

        }

    }

    return amount;

}