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defaultLoader.js
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(function(undefined) {
// The default loader is responsible for two things:
// 1. Maintaining the default in-memory registry of component configuration objects
// (i.e., the thing you're writing to when you call ko.components.register(someName, ...))
// 2. Answering requests for components by fetching configuration objects
// from that default in-memory registry and resolving them into standard
// component definition objects (of the form { createViewModel: ..., template: ... })
// Custom loaders may override either of these facilities, i.e.,
// 1. To supply configuration objects from some other source (e.g., conventions)
// 2. Or, to resolve configuration objects by loading viewmodels/templates via arbitrary logic.
var defaultConfigRegistry = {};
ko.components.register = function(componentName, config) {
if (!config) {
throw new Error('Invalid configuration for ' + componentName);
}
if (ko.components.isRegistered(componentName)) {
throw new Error('Component ' + componentName + ' is already registered');
}
defaultConfigRegistry[componentName] = config;
}
ko.components.isRegistered = function(componentName) {
return componentName in defaultConfigRegistry;
}
ko.components.unregister = function(componentName) {
delete defaultConfigRegistry[componentName];
ko.components.clearCachedDefinition(componentName);
}
ko.components.defaultLoader = {
'getConfig': function(componentName, callback) {
var result = defaultConfigRegistry.hasOwnProperty(componentName)
? defaultConfigRegistry[componentName]
: null;
callback(result);
},
'loadComponent': function(componentName, config, callback) {
var errorCallback = makeErrorCallback(componentName);
possiblyGetConfigFromAmd(errorCallback, config, function(loadedConfig) {
resolveConfig(componentName, errorCallback, loadedConfig, callback);
});
},
'loadTemplate': function(componentName, templateConfig, callback) {
resolveTemplate(makeErrorCallback(componentName), templateConfig, callback);
},
'loadViewModel': function(componentName, viewModelConfig, callback) {
resolveViewModel(makeErrorCallback(componentName), viewModelConfig, callback);
}
};
var createViewModelKey = 'createViewModel';
// Takes a config object of the form { template: ..., viewModel: ... }, and asynchronously convert it
// into the standard component definition format:
// { template: <ArrayOfDomNodes>, createViewModel: function(params, componentInfo) { ... } }.
// Since both template and viewModel may need to be resolved asynchronously, both tasks are performed
// in parallel, and the results joined when both are ready. We don't depend on any promises infrastructure,
// so this is implemented manually below.
function resolveConfig(componentName, errorCallback, config, callback) {
var result = {},
makeCallBackWhenZero = 2,
tryIssueCallback = function() {
if (--makeCallBackWhenZero === 0) {
callback(result);
}
},
templateConfig = config['template'],
viewModelConfig = config['viewModel'];
if (templateConfig) {
possiblyGetConfigFromAmd(errorCallback, templateConfig, function(loadedConfig) {
ko.components._getFirstResultFromLoaders('loadTemplate', [componentName, loadedConfig], function(resolvedTemplate) {
result['template'] = resolvedTemplate;
tryIssueCallback();
});
});
} else {
tryIssueCallback();
}
if (viewModelConfig) {
possiblyGetConfigFromAmd(errorCallback, viewModelConfig, function(loadedConfig) {
ko.components._getFirstResultFromLoaders('loadViewModel', [componentName, loadedConfig], function(resolvedViewModel) {
result[createViewModelKey] = resolvedViewModel;
tryIssueCallback();
});
});
} else {
tryIssueCallback();
}
}
function resolveTemplate(errorCallback, templateConfig, callback) {
if (typeof templateConfig === 'string') {
// Markup - parse it
callback(ko.utils.parseHtmlFragment(templateConfig));
} else if (templateConfig instanceof Array) {
// Assume already an array of DOM nodes - pass through unchanged
callback(templateConfig);
} else if (isDocumentFragment(templateConfig)) {
// Document fragment - use its child nodes
callback(ko.utils.makeArray(templateConfig.childNodes));
} else if (templateConfig['element']) {
var element = templateConfig['element'];
if (isDomElement(element)) {
// Element instance - copy its child nodes
callback(ko.utils.cloneNodes(element.childNodes));
} else if (typeof element === 'string') {
// Element ID - find it, then copy its child nodes
var elemInstance = document.getElementById(element);
if (elemInstance) {
callback(ko.utils.cloneNodes(elemInstance.childNodes));
} else {
errorCallback('Cannot find element with ID ' + element);
}
} else {
errorCallback('Unknown element type: ' + element);
}
} else {
errorCallback('Unknown template value: ' + templateConfig);
}
}
function resolveViewModel(errorCallback, viewModelConfig, callback) {
if (typeof viewModelConfig === 'function') {
// Constructor - convert to standard factory function format
// By design, this does *not* supply componentInfo to the constructor, as the intent is that
// componentInfo contains non-viewmodel data (e.g., the component's element) that should only
// be used in factory functions, not viewmodel constructors.
callback(function (params /*, componentInfo */) {
return new viewModelConfig(params);
});
} else if (typeof viewModelConfig[createViewModelKey] === 'function') {
// Already a factory function - use it as-is
callback(viewModelConfig[createViewModelKey]);
} else if ('instance' in viewModelConfig) {
// Fixed object instance - promote to createViewModel format for API consistency
var fixedInstance = viewModelConfig['instance'];
callback(function (params, componentInfo) {
return fixedInstance;
});
} else if ('viewModel' in viewModelConfig) {
// Resolved AMD module whose value is of the form { viewModel: ... }
resolveViewModel(errorCallback, viewModelConfig['viewModel'], callback);
} else {
errorCallback('Unknown viewModel value: ' + viewModelConfig);
}
}
function isDomElement(obj) {
if (window['HTMLElement']) {
return obj instanceof HTMLElement;
} else {
return obj && obj.tagName && obj.nodeType === 1;
}
}
function isDocumentFragment(obj) {
if (window['DocumentFragment']) {
return obj instanceof DocumentFragment;
} else {
return obj && obj.nodeType === 11;
}
}
function possiblyGetConfigFromAmd(errorCallback, config, callback) {
if (typeof config['require'] === 'string') {
// The config is the value of an AMD module
if (require || window['require']) {
(require || window['require'])([config['require']], callback);
} else {
errorCallback('Uses require, but no AMD loader is present');
}
} else {
callback(config);
}
}
function makeErrorCallback(componentName) {
return function (message) {
throw new Error('Component \'' + componentName + '\': ' + message);
};
}
ko.exportSymbol('components.register', ko.components.register);
ko.exportSymbol('components.isRegistered', ko.components.isRegistered);
ko.exportSymbol('components.unregister', ko.components.unregister);
// Expose the default loader so that developers can directly ask it for configuration
// or to resolve configuration
ko.exportSymbol('components.defaultLoader', ko.components.defaultLoader);
// By default, the default loader is the only registered component loader
ko.components['loaders'].push(ko.components.defaultLoader);
// Privately expose the underlying config registry for use in old-IE shim
ko.components._allRegisteredComponents = defaultConfigRegistry;
})();