以下两法方法都是实现textfield和textView的代理方法  需要先遵循代理

一：textField限制只能输入数字和小数点 且小数点后只能保留两位 小数点前最多5位 

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
    //  输入框中的值 只能输入到小数点后两位
     if (string.length == 0) {
        return YES;
     }
    const char * ch=[string cStringUsingEncoding:NSUTF8StringEncoding];
    if(*ch == 0)
        return YES;
    if( *ch != 46 && ( *ch<48 || *ch>57) )
        return NO;
    if([textField.text rangeOfString:@"."].length==1)
    {
        NSUInteger length=[textField.text rangeOfString:@"."].location;
        if([[textField.text substringFromIndex:length] length]>2 || *ch ==46)
            return NO;
    }else{
        NSInteger existedLength = textField.text.length;
        NSInteger selectedLength = range.length;
        NSInteger replaceLength = string.length;
        if (existedLength - selectedLength + replaceLength > 5&&![string isEqualToString: @"."]) {
            return NO;
        }
    }
    return YES;
}

二：textView限制输入字数，这里限制为25字以内

- (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text
{
    if ([text isEqualToString:@""] && range.length > 0) {
        return YES;
    }else {
        if (textView.text.length - range.length + text.length > 25) {
            return NO;
        }else {
            return YES;
        }
    }
}