- (NSString *)stringConvert:(NSString *)string{

//过滤不能打印的ASCII码

NSMutableString *str = [NSMutableString stringWithString:string];

for (int i = 0; i < str.length; i++) {

int ascii_code = [str characterAtIndex:i];

//31 之前的都是 ASCII中的控制符 128之后都是扩展字符 都是不可见字符 json 解析不了

NSRange range = NSMakeRange(i,1);

if (ascii_code <= 31 || (ascii_code>= 128 && ascii_code<=255)) {

[str deleteCharactersInRange:range];

--i;

}

}

return (NSString *)str;

}