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TiddlyWiki5/core/modules/widgets/let.js

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/*\
title: $:/core/modules/widgets/let.js
type: application/javascript
module-type: widget
This widget allows defining multiple variables at once, while allowing
the later variables to depend upon the earlier ones.
```
\define helloworld() Hello world!
<$let currentTiddler="target" value={{!!value}} currentTiddler="different">
{{!!value}} will be different from <<value>>
</$let>
```
\*/
(function(){
/*jslint node: true, browser: true */
/*global $tw: false */
"use strict";
var Widget = require("$:/core/modules/widgets/widget.js").widget;
var LetWidget = function(parseTreeNode,options) {
// Initialise
this.initialise(parseTreeNode,options);
};
/*
Inherit from the base widget class
*/
LetWidget.prototype = new Widget();
/*
Render this widget into the DOM
*/
LetWidget.prototype.render = function(parent,nextSibling) {
this.parentDomNode = parent;
this.computeAttributes();
this.execute();
this.renderChildren(parent,nextSibling);
};
LetWidget.prototype.computeAttributes = function() {
// Before computing attributes, we must make clear that none of the
// existing attributes are staged for lookup, even on a refresh
var changedAttributes = {},
self = this;
this.currentValueFor = Object.create(null);
$tw.utils.each($tw.utils.getOrderedAttributesFromParseTreeNode(this.parseTreeNode),function(attribute) {
var value = self.computeAttribute(attribute),
name = attribute.name;
// Now that it's prepped, we're allowed to look this variable up
// when defining later variables
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if(value !== undefined) {
self.currentValueFor[name] = value;
}
});
// Run through again, setting variables and looking for differences
$tw.utils.each(this.currentValueFor,function(value,name) {
if (self.attributes[name] !== value) {
self.attributes[name] = value;
self.setVariable(name,value);
changedAttributes[name] = true;
}
});
return changedAttributes;
};
LetWidget.prototype.getVariableInfo = function(name,options) {
// Special handling: If this variable exists in this very $let, we can
// use it, but only if it's been staged.
if ($tw.utils.hop(this.currentValueFor,name)) {
return {
text: this.currentValueFor[name]
};
}
return Widget.prototype.getVariableInfo.call(this,name,options);
};
/*
Refresh the widget by ensuring our attributes are up to date
*/
LetWidget.prototype.refresh = function(changedTiddlers) {
var changedAttributes = this.computeAttributes();
if($tw.utils.count(changedAttributes) > 0) {
this.refreshSelf();
return true;
}
return this.refreshChildren(changedTiddlers);
};
exports["let"] = LetWidget;
})();