UITextField : 限制输入时允许的最大值(数字)

问题描述

我有一个UITextField，我想限制该字段中允许的最大输入值为1000.那是当用户在里面输入数字时，一旦输入值大于999，除非用户输入小于 1000 的值，否则输入字段中的值将不再更新.

I have a UITextField, I'd like to restrict the maximum allowed input value in the field to be 1000. That's when user is inputting number inside, once the input value is larger than 999, the value in input field won't be updated anymore unless user is inputting value less than 1000.

我想我应该使用 UITextField 委托来限制输入:

I think I should use UITextField delegate to limit the input:

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
  //How to do
}

但我不确定如何实现它.有什么建议吗?

But I am not sure how to implement it. Any suggestions?

==========更新=============

我的输入框不仅允许用户输入整数，还可以输入浮点值，如 999,03

my input field not only allow user to input integer, but also float value like 999,03

推荐答案

你应该在上面的方法中做以下事情:

You should do the following inside the above method:

NSString *newString = [textField.text stringByReplacingCharactersInRange:range withString:string];

//first, check if the new string is numeric only. If not, return NO;
NSCharacterSet *characterSet = [[NSCharacterSet characterSetWithCharactersInString:@"0123456789,."] invertedSet];
if ([newString rangeOfCharacterFromSet:characterSet].location != NSNotFound)
{
    return NO;
}

return [newString doubleValue] < 1000;

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