无法分配给“ initialState”，因为它是只读属性

Question

Can't assign to a read-only property in constructor when it run in method,

the typescript version is 3.4.1

class Example {
   readonly initialState: any
   constructor(){
      this.someMethod()
   }
   private someMethod(){
     this.initialState = 'someState'
   }

}

Answer 1

readonly properties can only be initialized in place during declaration, or inside the constructor . The rationale here is that that method could potentially be called from somewhere else in your code, and attempt to set the property value again, so TypeScript blocks it entirely.

PS. I believe the code was just not copy-and-pasted correctly, since there's no setState() method in your class; your code would not run. I'm assuming you meant to say something like this.initialState = 'someState' . If you want to revise your question, there might be a different answer.