比较两个文本字段的文本

发布于 2024-11-27 15:58:11 字数 213 浏览 0 评论 0原文

如何比较两个文本字段中的文本以查看它们是否相同，例如“密码”和“确认密码”文本字段中的文本？

if (passwordField == passwordConfirmField) {

    //they are equal to each other

} else {

    //they are not equal to each other

}

原文

How do you compare the text in two text fields to see if they are the same, such as in "Password" and "Confirm Password" text fields?

if (passwordField == passwordConfirmField) {

    //they are equal to each other

} else {

    //they are not equal to each other

}

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千秋岁 2024-12-04 15:58:11

在 Objective-C 中，您应该使用 isEqualToString:，就像这样：

if ([passwordField.text isEqualToString:passwordConfirmField.text]) {
    //they are equal to each other
} else {
    //they are *not* equal to each other
}

NSString 是一个指针类型。当您使用 == 时，您实际上是在比较两个内存地址，而不是两个值。字段的 text 属性是 2 个不同的对象，具有不同的地址。
因此 == 将始终¹ 返回 false。

在 Swift 中情况有些不同。 Swift String 类型符合 Equatable 协议。这意味着它通过实现运算符 == 为您提供相等性。使以下代码可以安全使用：

let string1: String = "text"
let string2: String = "text"

if string1 == string2 {
    print("equal")
}

如果 string2 被声明为 NSString 会怎样？

let string2: NSString = "text"

由于 Swift 中 String 和 NSString 之间完成了一些桥接，因此 == 的使用仍然是安全的。

1：有趣的是，如果两个 NSString 对象具有相同的值，编译器可能会在后台进行一些优化并重新使用相同的对象。因此，在某些情况下可能==可能返回true。显然这不是您想要依赖的东西。

In Objective-C you should use isEqualToString:, like so:

if ([passwordField.text isEqualToString:passwordConfirmField.text]) {
    //they are equal to each other
} else {
    //they are *not* equal to each other
}

NSString is a pointer type. When you use == you are actually comparing two memory addresses, not two values. The text properties of your fields are 2 different objects, with different addresses.
So == will always¹ return false.

In Swift things are a bit different. The Swift String type conforms to the Equatable protocol. Meaning it provides you with equality by implementing the operator ==. Making the following code safe to use:

let string1: String = "text"
let string2: String = "text"

if string1 == string2 {
    print("equal")
}

And what if string2 was declared as an NSString?

let string2: NSString = "text"

The use of == remains safe, thanks to some bridging done between String and NSString in Swift.

1: Funnily, if two NSString object have the same value, the compiler may do some optimization under the hood and re-use the same object. So it is possible that == could return true in some cases. Obviously this not something you want to rely upon.

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伏妖词 2024-12-04 15:58:11

您可以通过使用 NSString 的 isEqualToString: 方法来做到这一点，如下所示：

NSString *password = passwordField.text;
NSString *confirmPassword = passwordConfirmField.text;

if([password isEqualToString: confirmPassword]) {
    // password correctly repeated
} else {
    // nope, passwords don't match
}

希望这会有所帮助！

You can do this by using the isEqualToString: method of NSString like so:

NSString *password = passwordField.text;
NSString *confirmPassword = passwordConfirmField.text;

if([password isEqualToString: confirmPassword]) {
    // password correctly repeated
} else {
    // nope, passwords don't match
}

Hope this helps!

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