mirror of
https://github.com/google/blockly.git
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98 lines
3.4 KiB
JavaScript
98 lines
3.4 KiB
JavaScript
/**
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* @license
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* Copyright 2019 Google LLC
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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/**
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* @fileoverview Fields can be created based on a JSON definition. This file
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* contains methods for registering those JSON definitions, and building the
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* fields based on JSON.
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* @author bekawestberg@gmail.com (Beka Westberg)
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*/
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'use strict';
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goog.provide('Blockly.fieldRegistry');
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/**
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* The set of all registered fields, keyed by field type as used in the JSON
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* definition of a block.
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* @type {!Object<string, !{fromJson: Function}>}
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* @private
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*/
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Blockly.fieldRegistry.typeMap_ = {};
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/**
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* Registers a field type.
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* Blockly.fieldRegistry.fromJson uses this registry to
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* find the appropriate field type.
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* @param {string} type The field type name as used in the JSON definition.
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* @param {!{fromJson: Function}} fieldClass The field class containing a
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* fromJson function that can construct an instance of the field.
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* @throws {Error} if the type name is empty, the field is already
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* registered, or the fieldClass is not an object containing a fromJson
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* function.
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*/
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Blockly.fieldRegistry.register = function(type, fieldClass) {
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if ((typeof type != 'string') || (type.trim() == '')) {
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throw Error('Invalid field type "' + type + '". The type must be a' +
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' non-empty string.');
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}
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if (Blockly.fieldRegistry.typeMap_[type]) {
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throw Error('Error: Field "' + type + '" is already registered.');
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}
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if (!fieldClass || (typeof fieldClass.fromJson != 'function')) {
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throw Error('Field "' + fieldClass + '" must have a fromJson function');
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}
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type = type.toLowerCase();
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Blockly.fieldRegistry.typeMap_[type] = fieldClass;
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};
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/**
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* Unregisters the field registered with the given type.
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* @param {string} type The field type name as used in the JSON definition.
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*/
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Blockly.fieldRegistry.unregister = function(type) {
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if (Blockly.fieldRegistry.typeMap_[type]) {
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delete Blockly.fieldRegistry.typeMap_[type];
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} else {
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console.warn('No field mapping for type "' + type +
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'" found to unregister');
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}
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};
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/**
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* Construct a Field from a JSON arg object.
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* Finds the appropriate registered field by the type name as registered using
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* Blockly.fieldRegistry.register.
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* @param {!Object} options A JSON object with a type and options specific
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* to the field type.
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* @return {Blockly.Field} The new field instance or null if a field wasn't
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* found with the given type name
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* @package
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*/
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Blockly.fieldRegistry.fromJson = function(options) {
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var type = options['type'].toLowerCase();
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var fieldClass = Blockly.fieldRegistry.typeMap_[type];
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if (!fieldClass) {
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console.warn('Blockly could not create a field of type ' + options['type'] +
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'. The field is probably not being registered. This could be because' +
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' the file is not loaded, the field does not register itself (Issue' +
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' #1584), or the registration is not being reached.');
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return null;
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}
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return fieldClass.fromJson(options);
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};
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