[Solved] Typescript generics and class properties

Question

When you redeclare the state property in Test, it gets a new type based on the type of the initializer, namely {bar: undefined}, as you can see by hovering over state. This is why TypeScript thinks that this.state.bar can’t be anything other than undefined, even after you checked that it was truthy. Initializing the state in the constructor is the correct solution.

Accepted Answer

When you redeclare the state property in Test, it gets a new type based on the type of the initializer, namely {bar: undefined}, as you can see by hovering over state. This is why TypeScript thinks that this.state.bar can’t be anything other than undefined, even after you checked that it was truthy. Initializing the state in the constructor is the correct solution.