What is the correct way to assign a property to a function's scope?

Question

What is the correct way to assign a property to a function's scope?

Lately, I've been delving into Typescript Decorators to address a specific issue in my application. Using a JS bridge to communicate TS code between Android and iOS, we currently define functions as follows:

index.js

import foo from './bar'

global.App = function() {
  this.foo = foo;
};

The above snippet enables the foo function to be accessed on the native side of the bridge.

I attempted to create a decorator for the foo method that would automatically "register" itself within global.App, but unfortunately, I didn't succeed in achieving this goal.

Below is the working decorator:

export const Task = (target, propertyKey, descriptor) => {
    let originalMethod = descriptor.value;
    descriptor.value = (...args) => originalMethod.apply(target, args);

    if (!global.App) {
        global.App = function () { 
            this.foo = descriptor.value;
        };
    }
    
    return descriptor;
}

Is there a way to add another method to the global.App function?

javascript typescript typescript-decorator

Answer 1

Answer №1

Primarily, the method named foo is added only once because upon the initial call of the decorator, global.App becomes defined and prevents re-entry into the code block that adds foo to global.App.

Additionally, with each subsequent call, global.App and foo are overwritten rather than being preserved for continued use.

To enable the possibility of adding multiple methods through repeated calls to the decorator, it would be necessary to introduce a new conditional branch in the code. This branch would handle the addition of methods after the initial call and dynamically assign the method name (likely passed as propertyKey to the decorator).

export const Task = (target, propertyKey, descriptor) => {
    let originalMethod = descriptor.value;
    descriptor.value = (...args) => originalMethod.apply(target, args);

    if (!global.App) {
        global.App = function () { 
            this[propertyKey] = descriptor.value;
        };
    } else {
        global.App[propertyKey] = descriptor.value;
    }
    
    return descriptor;
}

A modification similar to this concept could potentially resolve the issue at hand.

Answer 2

Primarily, the method named foo is added only once because upon the initial call of the decorator, global.App becomes defined and prevents re-entry into the code block that adds foo to global.App.

Additionally, with each subsequent call, global.App and foo are overwritten rather than being preserved for continued use.

To enable the possibility of adding multiple methods through repeated calls to the decorator, it would be necessary to introduce a new conditional branch in the code. This branch would handle the addition of methods after the initial call and dynamically assign the method name (likely passed as propertyKey to the decorator).

export const Task = (target, propertyKey, descriptor) => {
    let originalMethod = descriptor.value;
    descriptor.value = (...args) => originalMethod.apply(target, args);

    if (!global.App) {
        global.App = function () { 
            this[propertyKey] = descriptor.value;
        };
    } else {
        global.App[propertyKey] = descriptor.value;
    }
    
    return descriptor;
}

A modification similar to this concept could potentially resolve the issue at hand.

Answer 3

Answer №2

While exploring SO for a while, I managed to come up with a workaround for this issue. It's possible that my understanding of TS/JS is not as deep as it could be, but regardless, the solution I found involved registering every decorated task and then, in the index.js file, retrieving those tasks and registering them within the global.App function.

Here's an example:

task.ts

export const TaskRegistry = {};

 export const Task = (target, propertyKey, descriptor) => {
   const originalMethod = descriptor.value;
   descriptor.value = (...args) => originalMethod.apply(target, args);

   TaskRegistry[propertyKey] = descriptor.value;

   return descriptor;
 };

index.js

// eslint-disable-next-line func-names
global.App = function () {
   // eslint-disable-next-line consistent-this
   const self = this;

   Object.keys(TaskRegistry).forEach((key) => {
     self[key] = TaskRegistry[key];
   });
}

Answer 4

While exploring SO for a while, I managed to come up with a workaround for this issue. It's possible that my understanding of TS/JS is not as deep as it could be, but regardless, the solution I found involved registering every decorated task and then, in the index.js file, retrieving those tasks and registering them within the global.App function.

Here's an example:

task.ts

export const TaskRegistry = {};

 export const Task = (target, propertyKey, descriptor) => {
   const originalMethod = descriptor.value;
   descriptor.value = (...args) => originalMethod.apply(target, args);

   TaskRegistry[propertyKey] = descriptor.value;

   return descriptor;
 };

index.js

// eslint-disable-next-line func-names
global.App = function () {
   // eslint-disable-next-line consistent-this
   const self = this;

   Object.keys(TaskRegistry).forEach((key) => {
     self[key] = TaskRegistry[key];
   });
}

What is the correct way to assign a property to a function's scope?

Answer №1

Answer №2

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