Add action-deletefield widget

We’re also going to need action-deletetiddler

core/modules/widgets/action-deletefield.js

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+/*\
+title: $:/core/modules/widgets/action-deletefield.js
+type: application/javascript
+module-type: widget
+
+Action widget to delete fields of a tiddler.
+
+\*/
+(function(){
+
+/*jslint node: true, browser: true */
+/*global $tw: false */
+"use strict";
+
+var Widget = require("$:/core/modules/widgets/widget.js").widget;
+
+var DeleteFieldWidget = function(parseTreeNode,options) {
+	this.initialise(parseTreeNode,options);
+};
+
+/*
+Inherit from the base widget class
+*/
+DeleteFieldWidget.prototype = new Widget();
+
+/*
+Render this widget into the DOM
+*/
+DeleteFieldWidget.prototype.render = function(parent,nextSibling) {
+	this.computeAttributes();
+	this.execute();
+};
+
+/*
+Compute the internal state of the widget
+*/
+DeleteFieldWidget.prototype.execute = function() {
+	this.actionTiddler = this.getAttribute("$tiddler",this.getVariable("currentTiddler"));
+};
+
+/*
+Refresh the widget by ensuring our attributes are up to date
+*/
+DeleteFieldWidget.prototype.refresh = function(changedTiddlers) {
+	var changedAttributes = this.computeAttributes();
+	if(changedAttributes["$tiddler"]) {
+		this.refreshSelf();
+		return true;
+	}
+	return this.refreshChildren(changedTiddlers);
+};
+
+/*
+Invoke the action associated with this widget
+*/
+DeleteFieldWidget.prototype.invokeAction = function(triggeringWidget,event) {
+	var self = this,
+		tiddler = this.wiki.getTiddler(self.actionTiddler),
+		removeFields = {};
+	if(tiddler) {
+		$tw.utils.each(this.attributes,function(attribute,name) {
+			if(name.charAt(0) !== "$" && name !== "title") {
+				removeFields[name] = undefined;
+			}
+		});
+		this.wiki.addTiddler(new $tw.Tiddler(tiddler,removeFields));
+	}
+	return true; // Action was invoked
+};
+
+exports["action-deletefield"] = DeleteFieldWidget;
+
+})();

editions/prerelease/tiddlers/ActionDeleteFieldWidget.tid

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+caption: action-deletefield
+created: 20141025120850184
+modified: 20141025120850184
+tags: Widgets ActionWidgets
+title: ActionDeleteFieldWidget
+type: text/vnd.tiddlywiki
+
+! Introduction
+
+The ''action-deletefield'' widget is an [[action widget|ActionWidgets]] that deletes specified fields of a tiddler. ActionWidgets are used within triggering widgets such as the ButtonWidget.
+
+! Content and Attributes
+
+The ''action-deletefield'' widget is invisible. Any content within it is ignored.
+
+|!Attribute |!Description |
+|$tiddler |The title of the tiddler whose fields are to be modified (if not provided defaults to the [[WidgetVariable: currentTiddler]] |
+|//{any attributes not starting with $}// |Each attribute name specifies a field to be deleted. The attribute value is ignored and need not be specified |
+
+! Examples
+
+Here is an example of a button that deletes the caption and tags fields of the current tiddler:
+
+<$macrocall $name='wikitext-example-without-html'
+src='<$button>
+<$action-deletefield caption tags/>
+Delete "caption" and "tags"
+</$button>'/>
+
+Here is an example of a button that deletes the modified date and tags fields of the tiddler HelloThere:
+
+<$macrocall $name='wikitext-example-without-html'
+src='<$button>
+<$action-deletefield $tiddler="HelloThere" modified tags/>
+Delete "modified" and "tags" from ~HelloThere
+</$button>'/>