mframejs/dist/esm/binding/property/propertyObserverHandler.js

simple framework

import { traverseAST, getBehavior } from '../ast/traverseAst';
import { createBindingExpression, removeBindingExpression } from '../createBindingExpression';
import { ContainerBehavior } from '../../container/exported';
export class PropertyObserverHandler {
    constructor(expression, listener) {
        this.value = undefined;
        this.isNew = true;
        this.expression = expression;
        this.listener = listener;
    }
    bind(context) {
        this.observing = true;
        this.context = context;
        createBindingExpression(this.expression, this.context, this);
    }
    setAst(ast) {
        this.ast = ast;
        if (!this.curBehavior) {
            this.connectBehavior();
        }
    }
    init() {
        if (this.isNew) {
            this.isNew = false;
            const oldValue = this.value;
            const newValue = traverseAST(this.ast, this.context);
            this.value = newValue;
            this.listenerCall(newValue, oldValue);
            this.isNew = false;
        }
    }
    connectBehavior() {
        const behaviors = getBehavior(this.ast);
        if (behaviors) {
            behaviors.forEach((behavior) => {
                if (behavior.name === 'signal') {
                    const x = ContainerBehavior.findBehavior(behavior.name);
                    if (x) {
                        this.curBehavior = new x(this, behavior.args);
                    }
                }
            });
        }
    }
    update() {
        const newValue = traverseAST(this.ast, this.context);
        const oldValue = this.value;
        this.value = newValue;
        this.listenerCall(newValue, oldValue);
        this.bind(this.context);
    }
    listenerCall(newValue, oldValue) {
        if (this.listener) {
            this.listener.call(newValue, oldValue);
        }
    }
    unbind() {
        if (this.observing) {
            removeBindingExpression(this.expression, this.context, this);
        }
        this.listener.caller = null;
        this.observing = false;
        this.context = null;
        this.listener = null;
        this.value = null;
    }
}
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