javascript / expert
Snippet
Polymorphic State Pattern Architecture for Svelte Component Controllers
Implementing the classic Object-Oriented State design pattern replaces complex boolean conditional branches inside Svelte components with polymorphic class dispatching.
snippet.js
javascript
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class ViewState {render(controller) { throw new Error('Not implemented'); }}export class IdleState extends ViewState {render(controller) {return { label: 'Idle', canSubmit: false };}}export class ProcessingState extends ViewState {render(controller) {return { label: 'Working...', canSubmit: false };}}export class StateController {#currentState;constructor(initialState) {this.transitionTo(initialState);}transitionTo(state) {this.#currentState = state;}get current() {return this.#currentState.render(this);}}
svelte
Breakdown
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class ViewState {
Establishes a base abstract state class defining common polymorphic behaviors.
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export class ProcessingState extends ViewState {
Concrete state implementation representing the active asynchronous processing state.
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this.#currentState = state;
Encapsulates the current active state instance inside the context manager class.
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return this.#currentState.render(this);
Delegates UI state calculation polymorphically based on the current state class type.