如何将 String? 类型的对象分配给 String 类型的变量? [英] How do you assign a String?-type object to a String-type variable?

问题描述

我想将字典的 value 元素分配给 String 变量.

I would like to assign the value element of a dictionary to a String variable.

在swiftUI 中，字典中的所有值元素都以String 形式返回?类型.

In swiftUI, all value elements in dictionaries are returned as String? type.

当一个字符串?type 分配给 String 变量，该 String 变量在 swiftUI 应用程序中显示为 Optional("theStringIamTryingToDisplay").

When a String? type is assigned to a String variable, the String variable displays in the swiftUI app as Optional("theStringIamTryingToDisplay").

我如何摆脱可选"在应用程序显示中?

How do I get rid of the "Optional" in the app display?

推荐答案

您必须首先确保变量实际上不包含 nil.您可以通过多种方式做到这一点 - 可能会很好阅读:

You'll have to first make sure that the variable doesn't in fact contain nil. You can do that in a number of ways -- might be good to read:

• Swift:为 nil 测试可选项
• https://www.hackingwithswift.com/articles/136/the-complete-guide-to-optionals-in-swift
• https://docs.swift.org/swift-book/LanguageGuide/TheBasics.html

一种方法是通过可选绑定:

One way is by optional binding:

if let myVariable = myDictionary["key"] {
  Text(myVariable)
}

另一个是提供一个默认值:

Another is to provide an default value:

Text("My result: \(myDictionary["key"] ?? "default value")

还有其他可能性，但这些以及上面的链接应该可以帮助您入门.

There are other possibilities, but these, plus the links above, should get you started.

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