Objective-C如何限制文本字段在2次输入后只允许特定字符

Posted 2023-03-11

【中文标题】Objective-C如何限制文本字段在2次输入后只允许特定字符

【英文标题】：Objective-C How to restrict text field to only allow a specific character after 2 inputs

【发布时间】：2017-09-29 09:30:11

【问题描述】：

我有一个文本字段，我应该只允许 2 位数字，最多 2 位小数（例如 25.50）。我想限制 3 个字符的输入。在我的情况下，如果有 2 个输入并且它们都不是句点“。”它应该只允许第三个输入的时间。

我在此文本字段中使用数字键盘，这意味着唯一可用的输入是数字 0 到 9 和句点，您可以在上传的屏幕截图中看到。

以下是我用于其他限制的代码，以及我假设代码需要满足我需要的部分。其他一切正常。

- (BOOL) textView:(UITextView *)sender shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)string


//set to possibly restrict the character .
NSMutableCharacterSet *mcs1 = [[NSCharacterSet letterCharacterSet] mutableCopy];
[mcs1 addCharactersInString:@"."];
NSMutableCharacterSet *mcs2 = [[NSCharacterSet letterCharacterSet] mutableCopy];/    
[mcs2 addCharactersInString:@"123456789"];

// allow only one period to be inserted
NSRange temprange = [sender.text rangeOfString:@"."];

    if ((temprange.location != NSNotFound) && [string isEqualToString:@"."])
    
        return NO;
    

// allow to use backspace and overlap code below
if ([string isEqualToString:@""]) 
    return YES;




// a max of 5 characters
if(sender.text.length == 5)

    return NO;

// if there are 2 inputs and none of them is a period
if(sender.text.length == 2 && [sender.text rangeOfCharacterFromSet:mcs1].location == NSNotFound) 

    // NEEDED CODE
    

// allow only 2 decimal places after a period
NSString *newString = [sender.text stringByReplacingCharactersInRange:range withString:string];
NSArray *sep = [newString componentsSeparatedByString:@"."];
if([sep count] >= 2)

    NSString *sepStr=[NSString stringWithFormat:@"%@",[sep objectAtIndex:1]];
    return !([sepStr length]>2);

return YES;

【问题讨论】：

使用正则表达式或浮点验证取决于您的选择

【参考方案1】：

这是我的问题的解决方案。我修改了您的建议，现在它适用于我目前正在使用的所有其他限制。 ACCEPTABLE_CHARACTERS 是在一个不同的类中定义的，我有我的所有常量。非常感谢:)

#define ACCEPTABLE_CHARACTERS @"."     
- (BOOL) textView:(UITextView *)sender shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)string

//set to possibly restrict the character .
NSMutableCharacterSet *mcs1 = [[NSCharacterSet letterCharacterSet] mutableCopy];
[mcs1 addCharactersInString:@"."];

// allow only one period to be inserted
NSRange temprange = [sender.text rangeOfString:@"."];

    if ((temprange.location != NSNotFound) && [string isEqualToString:@"."])
    
        return NO;
    

// allow to use backspace and overlap code below
if ([string isEqualToString:@""]) 
    return YES;


// allow only a period as the third input
    if (sender.text.length < 2 || string.length == 0)
    return YES;

else if (sender.text.length == 2 && [sender.text rangeOfCharacterFromSet:mcs1].location == NSNotFound)

    NSCharacterSet *cs = [[NSCharacterSet characterSetWithCharactersInString:ACCEPTABLE_CHARACTERS] invertedSet];

    NSString *filtered = [[string componentsSeparatedByCharactersInSet:cs] componentsJoinedByString:@""];

    return [string isEqualToString:filtered];



// a max of 5 characters (not needed but it should stay)
if(sender.text.length == 5)

    return NO;



// allow only 2 decimal places after a period

NSString *newString = [sender.text stringByReplacingCharactersInRange:range withString:string];
NSArray *sep = [newString componentsSeparatedByString:@"."];
if([sep count] >= 2)
    
    NSString *sepStr=[NSString stringWithFormat:@"%@",[sep objectAtIndex:1]];
    return !([sepStr length]>2);
    

【参考方案2】：

给你

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string 
    if (textField == txtEmailAdd) // Change with your TextField object 
        NSUInteger newLength = [textField.text length] + [string length] - range.length;

        if (newLength == 3 && ![textField.text containsString:@"."]) 
            textField.text = [NSString stringWithFormat:@"%@.", textField.text];
        
        else if (newLength == 3 && [textField.text containsString:@"."]) 
            textField.text = [textField.text stringByReplacingOccurrencesOfString:@"." withString:@""];
        

        return newLength <=5;
    
    return YES;

【参考方案3】：

结合我的编辑和某人的建议提出的解决方案。

#define ACCEPTABLE_CHARACTERS @"."     
- (BOOL) textView:(UITextView *)sender shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)string

//set to possibly restrict the character .
NSMutableCharacterSet *mcs1 = [[NSCharacterSet letterCharacterSet] mutableCopy];
[mcs1 addCharactersInString:@"."];

// allow only one period to be inserted
NSRange temprange = [sender.text rangeOfString:@"."];

if ((temprange.location != NSNotFound) && [string isEqualToString:@"."])

    return NO;


// allow to use backspace and overlap code below
if ([string isEqualToString:@""]) 
return YES;


// allow only a period as the third input
if (sender.text.length < 2 || string.length == 0)
return YES;

else if (sender.text.length == 2 && [sender.text rangeOfCharacterFromSet:mcs1].location == NSNotFound)

NSCharacterSet *cs = [[NSCharacterSet characterSetWithCharactersInString:ACCEPTABLE_CHARACTERS] invertedSet];

NSString *filtered = [[string componentsSeparatedByCharactersInSet:cs] componentsJoinedByString:@""];

return [string isEqualToString:filtered];



// a max of 5 characters (not needed but it should stay)
if(sender.text.length == 5)

return NO;



// allow only 2 decimal places after a period

NSString *newString = [sender.text stringByReplacingCharactersInRange:range withString:string];
NSArray *sep = [newString componentsSeparatedByString:@"."];
if([sep count] >= 2)

NSString *sepStr=[NSString stringWithFormat:@"%@",[sep objectAtIndex:1]];
return !([sepStr length]>2);