Question

I would like to have constant (readonly) properties in a React.Component class. The problem is that I should not initialize them in the constructor since they trigger side effects like setInterval or fetch. Instead I should initialize them in componentDidMount but since I use strict type checkings I must also indicate their types can be undefined (or null, whatsoever). That s what I want to avoid because then I am forced to check if the value is not null every time I use it despite I know it already, and I also wanna avoid using the "!" operator as much as possible because then I don t have type errors when I forget to initialize them.

Does there exist a clean solution? Some way to tell typescript that componentDidMount is like a constructor and so a property can be initialized only there?

Answer 1

没有,也没有这样做的干净方法。字典对班级的理解有其内在的特性,即班级大约有两个领域:(与问题无关):

The constructor: where fields -and their backing types- are being initialized
The rest of the class: where fields are being used - and their backing types don t change

退一步:知道<代码>componentDidMount<>/code>是一种初始化功能,类似于编码中的“隐蔽假设”。这就是说,它不是贾瓦古典的一部分,法典本身也没有解释这一点。你们在从事重修班时会知道什么。缺乏良好工具的类型系统是因为很难在类型系统地描述每个框架的细微差别。

由于许多开发商迁到,因此,这些隐蔽的假设已经破灭。它们不需要随着时间的推移而改变财产类型——它更多地围绕变量和范围,而后者更适合类型系统。

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