清除UITextField的最佳方法

For an IBOutlet UITextField, does it matter as far as memory management or other reasons how you clear the text value?

对于IBOutlet UITextField，在内存管理或其他原因如何清除文本值方面是否重要？

textFieldX.text = nil

要么

textFieldX.text = @"";

In objective-c it is acceptable to message a nil object and @"" is a static NSString *. I'm not sure if every @"" points to the same object in memory or if it allocates a bunch of 1 byte null terminated strings.

在objective-c中，可以发送一个nil对象，而@“”是一个静态的NSString *。我不确定每个@“”是否指向内存中的同一个对象，或者它是否分配了一堆1字节的空终止字符串。

Not a big deal, just thought I'd ask the community. Thanks.

没什么大不了的，只是想我会问社区。谢谢。

5 个解决方案

#1

Personally I would think less of the memory usage here and more on code-maintainability.

就个人而言，我会更少考虑这里的内存使用情况，更多地考虑代码可维护性。

To me, It makes sense that a label always has a string. In the future someone might try to append a labels value, save it in a database, wrap it in xml, etc. An empty NSString in this case makes much more sense to me that a 0x0.

对我来说，标签总是有一个字符串是有道理的。在将来，有人可能会尝试附加标签值，将其保存在数据库中，将其包装在xml中等等。在这种情况下，空NSString对我来说更有意义，即0x0。

#2

I usually do textFieldX.text = @""; just for clarity. This helps me remember that the value should be a string, and that I can pass it all the standard string methods.

我通常做textFieldX.text = @“”;为了清楚起见。这有助于我记住该值应该是一个字符串，并且我可以将所有标准字符串方法传递给它。

#3

I recommend you to use nil, because I discovered that when you use @"", the placeholder is not aligned in the center(if it must be aligned). Look, how I changed my code to get placeholder aligned properly.

我建议你使用nil，因为我发现当你使用@“”时，占位符没有在中心对齐（如果它必须对齐）。看，我是如何更改代码以使占位符正确对齐的。

 wordTextField.textAlignment = UITextAlignmentCenter;
 //wordTextField.text = @"";
 wordTextField.text = nil;
 translationTextField.textAlignment = UITextAlignmentCenter;
 //translationTextField.text = @"";
 translationTextField.text = nil;

#4

Strings always copy in Objective-C, so the second option is most likely creating another string, and then pointing to it. In that way, I think you're right.

字符串总是在Objective-C中复制，因此第二个选项很可能是创建另一个字符串，然后指向它。这样，我认为你是对的。

To play devil's advocate, I would assume that the compiler optimizes option B to do something like option A anyway. Personally, I would always do option B because it's more readable as far as the end operation you want to accomplish.

为了扮演魔鬼的拥护者，我认为编译器会优化选项B以执行类似选项A的操作。就个人而言，我总是会做选项B，因为就你想要完成的最终操作而言，它更具可读性。

UPDATE: I didn't find a way to accomplish your goal differently, but you may be interested in this tidbit (from Apple UITextField Docs):

更新：我没有找到以不同方式实现目标的方法，但您可能对这个花絮感兴趣（来自Apple UITextField Docs）：

clearButtonMode

clearButtonMode

Controls when the standard clear button appears in the text field.

控制标准清除按钮何时出现在文本字段中。

@property(nonatomic) UITextFieldViewMode clearButtonMode

@property（非原子）UITextFieldViewMode clearButtonMode

Discussion

讨论

The standard clear button is displayed at the right side of the text field as a way for the user to remove text quickly. This button appears automatically based on the value set for this property.

标准清除按钮显示在文本字段的右侧，以便用户快速删除文本。此按钮基于为此属性设置的值自动显示。

The default value for this property is UITextFieldViewModeNever.

此属性的默认值为UITextFieldViewModeNever。

I think this would allow you to setup functionality for the user to clear the text field.

我认为这将允许您为用户设置清除文本字段的功能。

#5

I find that using textField.text = nil; has an undesirable effect on my project. I am building a calculator.

我发现使用textField.text = nil;对我的项目有不良影响。我正在建一个计算器。

When using the above code, after I press the clear button, pressing a digit does not come up on screen.

使用上述代码时，按下清除按钮后，屏幕上不会显示数字。

textField.text = @"";

works good for me.

对我有益。

#1