What strategies can I use to address the issue of requiring a type before it has been defined?

Encountered an intriguing challenge. Here are the types I'm working with:

export interface QuestionPrimative {
    question    : string;
    id          : string;
    name        : string;
    formctrl?   : string;
    formgrp?    : string;
    lowExtreme? : string;
    hiExtreme?  : string;
    template    : string;
}

export interface Answer {
    answer      : string;
    id          : string;
    trigger?    : string;
    formctrl?   : string;
}

export interface QuestionBase extends QuestionPrimative {
    answers?: Answer[];
}

export interface MicroQuestions {
    activate?   : string;
    questions?  : QuestionBase[];  // Prefer this as Question[]
}

export interface Question extends QuestionBase {
    micros? : MicroQuestions[];
}

Loading this into a custom Angular 2 Component designed to handle various types of questions automatically. To provide a clearer explanation and reasoning behind the structure, here is a commented version of the entire model:

// Data iteration in Component
question    : string;           
id          : string;           
name        : string;           
formctrl?   : string;           
formgrp?    : string;           
template    : string;           
answers?    : Answer[];         
lowExtreme? : string;           
hiExtreme?  : string;           
micros?     : MicroQuestions[]; 

// If answers exist.....
answer      : string;           
id          : string;          
trigger?    : string;          
formctrl?   : string;          

// If additional questions exist......
activate?   : string;           
questions?  : QuestionBase[];   

Any suggestions on how to properly type this for effective looping?

Answer №1

To make it function correctly, simply substitute QuestionBase for Question:

export interface QuestionPrimative {
  question: string;
  id: string;
  name: string;
  formctrl?: string;
  formgrp?: string;
  lowExtreme?: string;
  hiExtreme?: string;
  template: string;
}

export interface Answer {
  answer: string;
  id: string;
  trigger?: string;
  formctrl?: string;
}

export interface Question extends QuestionPrimative {
  answers?: Answer[];
}

export interface MicroQuestions {
  activate?: string;
  questions?: Question[];  // Works
}

export interface QuestionBase extends Question {
  micros?: MicroQuestions[];
}

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