Tips for creating a TypeScript-compatible redux state tree with static typing and immutability:

Question

Tips for creating a TypeScript-compatible redux state tree with static typing and immutability:

One remarkable feature of TypeScript + Redux is the ability to define a statically typed immutable state tree in the following manner:


        interface StateTree {
          readonly subState1: SubState1;
          readonly subState2: SubState2;
        }

        interface SubState1 {
          readonly a: number;
          readonly b: string;
        }

        interface SubState2 {
          readonly c: {
            readonly d: symbol;
            readonly e: string;
          };
        }

This approach eliminates the need for libraries like ImmutableJS and provides strong guarantees when accessing the read-only state tree, as shown here:


        const state: StateTree = getState();
        state.subState2.c.e

However, the question arises: Is there a method to maintain immutability and type-safety while creating modified copies of these read-only state trees?

I initially considered using Object.assign(), which ensures immutability but lacks compile-time type-safety due to TypeScript's behavior with type intersection (refer to this discussion).

javascript typescript redux

Answer 1

Answer №1

When I initially set up my React & Redux project, I overlooked the importance of immutability. Now, I'm faced with the task of retroactively incorporating it into my codebase. As I explore different approaches, I prioritize maintaining TypeScript's strong typing capabilities. While Immutable.js didn't seem to offer a seamless solution for type checking in my project, I came across a promising alternative: ImmutableAssign.

https://github.com/engineforce/ImmutableAssign

ImmutableAssign aims to integrate effectively with TypeScript, which aligns perfectly with my requirements. So far, it appears to meet my expectations by updating references throughout nested objects when a property is modified deep within the chain. However, as I continue implementing ImmutableAssign in my project, I have yet to assess its performance characteristics. Nonetheless, it's worth exploring this tool as you navigate similar challenges.

Answer 2

When I initially set up my React & Redux project, I overlooked the importance of immutability. Now, I'm faced with the task of retroactively incorporating it into my codebase. As I explore different approaches, I prioritize maintaining TypeScript's strong typing capabilities. While Immutable.js didn't seem to offer a seamless solution for type checking in my project, I came across a promising alternative: ImmutableAssign.

https://github.com/engineforce/ImmutableAssign

ImmutableAssign aims to integrate effectively with TypeScript, which aligns perfectly with my requirements. So far, it appears to meet my expectations by updating references throughout nested objects when a property is modified deep within the chain. However, as I continue implementing ImmutableAssign in my project, I have yet to assess its performance characteristics. Nonetheless, it's worth exploring this tool as you navigate similar challenges.

Answer 3

Answer №2

Using the "readonly" keyword is an important feature when striving for immutability, but it only takes effect during compilation.

When working with immutable.js, you take a step further as it ensures immutability at runtime.

While there isn't a one-size-fits-all solution that combines deep cloning and type safety perfectly, Object.assign does provide shallow copying which often suffices when managing states in Redux.

I don't believe that using Object.assign compromises compile-time safety. The structural typing system in Typescript verifies compatibility by ensuring that all required members are assigned properly. For example:

interface State {
    a: number;
}

const myVar = Object.assign({}, {b: 456}) as State;

In this case, the code will fail to compile because a is missing in myVar.

Answer 4

Using the "readonly" keyword is an important feature when striving for immutability, but it only takes effect during compilation.

When working with immutable.js, you take a step further as it ensures immutability at runtime.

While there isn't a one-size-fits-all solution that combines deep cloning and type safety perfectly, Object.assign does provide shallow copying which often suffices when managing states in Redux.

I don't believe that using Object.assign compromises compile-time safety. The structural typing system in Typescript verifies compatibility by ensuring that all required members are assigned properly. For example:

interface State {
    a: number;
}

const myVar = Object.assign({}, {b: 456}) as State;

In this case, the code will fail to compile because a is missing in myVar.

Answer 5

Answer №3

Upon careful consideration of the discussion provided at the mentioned link, I have come to realize that my initial belief regarding the limitations of Object.assign() in TypeScript due to type intersection was actually unfounded. The true underlying issue lies with object assignment itself.

The actual problem stems from object assignment rather than type intersection in TypeScript.

I had mistakenly attributed the issue to type intersection when it is clearly rooted in object assignment:

interface Combined {
  a: number;
  b: string;
}

interface A {
  a: number;
}

interface B {
  b: string;
}

const temp1: Combined = {
  a: 1,
  b: '2'
};

const temp2: A = temp1;

This scenario does not involve any type intersection.

An interface should be viewed as just that – an interface, not a concrete type.

In reference to the code snippet above, my confusion around the validity of the statement const temp: A = temp1; arose from a misconception rooted in type intersection.

However, upon closer inspection, I now understand the rationale behind its validation.

The A interface is not a tangible type like a primitive or a class; rather, it serves as an interface.

Final Thoughts

In summary...

TypeScript's effective utilization of interface and readonly, combined with JavaScript's Object.assign(), provide optimal compile-time type safety and immutability.

While these tools offer substantial support, the responsibility for further verification primarily rests on practices such as unit testing and code review.

Answer 6

Upon careful consideration of the discussion provided at the mentioned link, I have come to realize that my initial belief regarding the limitations of Object.assign() in TypeScript due to type intersection was actually unfounded. The true underlying issue lies with object assignment itself.

The actual problem stems from object assignment rather than type intersection in TypeScript.

I had mistakenly attributed the issue to type intersection when it is clearly rooted in object assignment:

interface Combined {
  a: number;
  b: string;
}

interface A {
  a: number;
}

interface B {
  b: string;
}

const temp1: Combined = {
  a: 1,
  b: '2'
};

const temp2: A = temp1;

This scenario does not involve any type intersection.

An interface should be viewed as just that – an interface, not a concrete type.

In reference to the code snippet above, my confusion around the validity of the statement const temp: A = temp1; arose from a misconception rooted in type intersection.

However, upon closer inspection, I now understand the rationale behind its validation.

The A interface is not a tangible type like a primitive or a class; rather, it serves as an interface.

Final Thoughts

In summary...

TypeScript's effective utilization of interface and readonly, combined with JavaScript's Object.assign(), provide optimal compile-time type safety and immutability.

While these tools offer substantial support, the responsibility for further verification primarily rests on practices such as unit testing and code review.

Tips for creating a TypeScript-compatible redux state tree with static typing and immutability:

Answer №1

Answer №2

Answer №3

The actual problem stems from object assignment rather than type intersection in TypeScript.

An interface should be viewed as just that – an interface, not a concrete type.

Final Thoughts

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