instantiate.js

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 Copyright (c) 2013-2016 Chukong Technologies Inc.
 Copyright (c) 2017-2018 Xiamen Yaji Software Co., Ltd.

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 Permission is hereby granted, free of charge, to any person obtaining a copy
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  used for developing games. You are not granted to publish, distribute,
  sublicense, and/or sell copies of Cocos Creator.

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var CCObject = require('./CCObject');
var CCValueType = require('../value-types/value-type');
var Destroyed = CCObject.Flags.Destroyed;
var PersistentMask = CCObject.Flags.PersistentMask;
var _isDomNode = require('./utils').isDomNode;

/**
 * !#en Clones the object `original` and returns the clone, or instantiate a node from the Prefab.
 * !#zh 克隆指定的任意类型的对象，或者从 Prefab 实例化出新节点。
 *
 * （Instantiate 时，function 和 dom 等非可序列化对象会直接保留原有引用，Asset 会直接进行浅拷贝，可序列化类型会进行深拷贝。）
 *
 * @method instantiate
 * @param {Prefab|Node|Object} original - An existing object that you want to make a copy of.
 * @return {Node|Object} the newly instantiated object
 * @typescript
 * instantiate(original: Prefab): Node
 * instantiate<T>(original: T): T
 * @example
 * // instantiate node from prefab
 * var scene = cc.director.getScene();
 * var node = cc.instantiate(prefabAsset);
 * node.parent = scene;
 * // clone node
 * var scene = cc.director.getScene();
 * var node = cc.instantiate(targetNode);
 * node.parent = scene;
 */
function instantiate (original, internal_force) {
    if (!internal_force) {
        if (typeof original !== 'object' || Array.isArray(original)) {
            if (CC_DEV) {
                cc.errorID(6900);
            }
            return null;
        }
        if (!original) {
            if (CC_DEV) {
                cc.errorID(6901);
            }
            return null;
        }
        if (!cc.isValid(original)) {
            if (CC_DEV) {
                cc.errorID(6902);
            }
            return null;
        }
        if (CC_DEV && original instanceof cc.Component) {
            cc.warn('Should not instantiate a single cc.Component directly, you must instantiate the entire node.');
        }
    }

    var clone;
    if (original instanceof CCObject) {
        // Invoke _instantiate method if supplied.
        // The _instantiate callback will be called only on the root object, its associated object will not be called.
        // @callback associated
        // @param {Object} [instantiated] - If supplied, _instantiate just need to initialize the instantiated object,
        //                                  no need to create new object by itself.
        // @returns {Object} - the instantiated object
        if (original._instantiate) {
            cc.game._isCloning = true;
            clone = original._instantiate();
            cc.game._isCloning = false;
            return clone;
        }
        else if (original instanceof cc.Asset) {
            // 不允许用通用方案实例化资源
            if (CC_DEV) {
                cc.errorID(6903);
            }
            return null;
        }
    }

    cc.game._isCloning = true;
    clone = doInstantiate(original);
    cc.game._isCloning = false;
    return clone;
}

var objsToClearTmpVar = [];   // used to reset _iN$t variable

///**
// * Do instantiate object, the object to instantiate must be non-nil.
// * 这是一个通用的 instantiate 方法，可能效率比较低。
// * 之后可以给各种类型重写快速实例化的特殊实现，但应该在单元测试中将结果和这个方法的结果进行对比。
// * 值得注意的是，这个方法不可重入。
// *
// * @param {Object} obj - 该方法仅供内部使用，用户需负责保证参数合法。什么参数是合法的请参考 cc.instantiate 的实现。
// * @param {Node} [parent] - 只有在该对象下的场景物体会被克隆。
// * @return {Object}
// * @private
// */
function doInstantiate (obj, parent) {
    if (Array.isArray(obj)) {
        if (CC_DEV) {
            cc.errorID(6904);
        }
        return null;
    }
    if (_isDomNode && _isDomNode(obj)) {
        if (CC_DEV) {
            cc.errorID(6905);
        }
        return null;
    }

    var clone;
    if (obj._iN$t) {
        // User can specify an existing object by assigning the "_iN$t" property.
        // enumerateObject will always push obj to objsToClearTmpVar
        clone = obj._iN$t;
    }
    else if (obj.constructor) {
        var klass = obj.constructor;
        clone = new klass();
    }
    else {
        clone = Object.create(null);
    }

    enumerateObject(obj, clone, parent);

    for (var i = 0, len = objsToClearTmpVar.length; i < len; ++i) {
        objsToClearTmpVar[i]._iN$t = null;
    }
    objsToClearTmpVar.length = 0;

    return clone;
}

// @param {Object} obj - The object to instantiate, typeof must be 'object' and should not be an array.

function enumerateCCClass (klass, obj, clone, parent) {
    var props = klass.__values__;
    for (var p = 0; p < props.length; p++) {
        var key = props[p];
        var value = obj[key];
        if (typeof value === 'object' && value) {
            var initValue = clone[key];
            if (initValue instanceof CCValueType &&
                initValue.constructor === value.constructor) {
                initValue.set(value);
            }
            else {
                clone[key] = value._iN$t || instantiateObj(value, parent);
            }
        }
        else {
            clone[key] = value;
        }
    }
}

function enumerateObject (obj, clone, parent) {
    // 目前使用“_iN$t”这个特殊字段来存实例化后的对象，这样做主要是为了防止循环引用
    // 注意，为了避免循环引用，所有新创建的实例，必须在赋值前被设为源对象的_iN$t
    obj._iN$t = clone;
    objsToClearTmpVar.push(obj);
    var klass = obj.constructor;
    if (cc.Class._isCCClass(klass)) {
        enumerateCCClass(klass, obj, clone, parent);
    }
    else {
        // primitive javascript object
        for (var key in obj) {
            if (!obj.hasOwnProperty(key) ||
                (key.charCodeAt(0) === 95 && key.charCodeAt(1) === 95 &&   // starts with "__"
                 key !== '__type__')
            ) {
                continue;
            }
            var value = obj[key];
            if (typeof value === 'object' && value) {
                if (value === clone) {
                    continue;   // value is obj._iN$t
                }
                clone[key] = value._iN$t || instantiateObj(value, parent);
            }
            else {
                clone[key] = value;
            }
        }
    }
    if (obj instanceof CCObject) {
        clone._objFlags &= PersistentMask;
    }
}

/*
 * @param {Object|Array} obj - the original non-nil object, typeof must be 'object'
 * @return {Object|Array} - the original non-nil object, typeof must be 'object'
 */
function instantiateObj (obj, parent) {
    if (obj instanceof CCValueType) {
        return obj.clone();
    }
    if (obj instanceof cc.Asset) {
        // 所有资源直接引用，不需要拷贝
        return obj;
    }
    var clone;
    if (Array.isArray(obj)) {
        var len = obj.length;
        clone = new Array(len);
        obj._iN$t = clone;
        for (var i = 0; i < len; ++i) {
            var value = obj[i];
            if (typeof value === 'object' && value) {
                clone[i] = value._iN$t || instantiateObj(value, parent);
            }
            else {
                clone[i] = value;
            }
        }
        objsToClearTmpVar.push(obj);
        return clone;
    }
    else if (obj._objFlags & Destroyed) {
        // the same as cc.isValid(obj)
        return null;
    }

    var ctor = obj.constructor;
    if (cc.Class._isCCClass(ctor)) {
        if (parent) {
            if (parent instanceof cc.Component) {
                if (obj instanceof cc._BaseNode || obj instanceof cc.Component) {
                    return obj;
                }
            }
            else if (parent instanceof cc._BaseNode) {
                if (obj instanceof cc._BaseNode) {
                    if (!obj.isChildOf(parent)) {
                        // should not clone other nodes if not descendant
                        return obj;
                    }
                }
                else if (obj instanceof cc.Component) {
                    if (!obj.node.isChildOf(parent)) {
                        // should not clone other component if not descendant
                        return obj;
                    }
                }
            }
        }
        clone = new ctor();
    }
    else if (ctor === Object) {
        clone = {};
    }
    else if (!ctor) {
        clone = Object.create(null);
    }
    else {
        // unknown type
        return obj;
    }
    enumerateObject(obj, clone, parent);
    return clone;
}

instantiate._clone = doInstantiate;
cc.instantiate = instantiate;
module.exports = instantiate;