mungedb-aggregate/lib/pipeline/expressions/SetEqualsExpression.js

"use strict";

/**
 * A $setequals pipeline expression.
 * @see evaluateInternal
 * @class SetEqualsExpression
 * @namespace mungedb-aggregate.pipeline.expressions
 * @module mungedb-aggregate
 * @constructor
 **/
var SetEqualsExpression = module.exports = function SetEqualsExpression() {
    this.nargs = 2;
    if (arguments.length !== 2) throw new Error("two args expected");
    base.call(this);
}, klass = SetEqualsExpression,
    base = require("./NaryExpression"),
    proto = klass.prototype = Object.create(base.prototype, {
        constructor: {
            value: klass
        }
    });

// DEPENDENCIES
var Value = require("../Value"),
                Expression = require("./Expression");

// PROTOTYPE MEMBERS
proto.getOpName = function getOpName() {
                return "$setequals";
};

/**
 * Takes 2 arrays. Assigns the second array to the first array.
 * @method evaluateInternal
 **/
proto.evaluateInternal = function evaluateInternal(vars) {
                var array1 = this.operands[0].evaluateInternal(vars),
                                array2 = this.operands[1].evaluateInternal(vars);
                if (array1 instanceof Array) throw new Error(this.getOpName() + ": object 1 must be an array");
                if (array2 instanceof Array) throw new Error(this.getOpName() + ": object 2 must be an array");
                array1 = array2;
                return array1;
};

/** Register Expression */
Expression.registerExpression("$setequals", base.parse(SetEqualsExpression));