1 % The MasterKey Widget Set developer's guide
12 Development with MKWS consists primarily of defining new types of
13 widgets. These can interact with the core functionality is several
16 You create a new widget type by calling the `mkws.registerWidgetType`
17 function, passing in the widget name and a function. The name is used
18 to recognise HTML elements as being widgets of this type -- for
19 example, if you register a `Foo` widget, elements like
20 `<div class="mkwsFoo">` will be widgets of this type.
22 The function promotes a bare widget object (passed as `this`) into a
23 widget of the appropriate type. MKWS doesn't use classes or explicit
24 prototypes: it just makes objects that have the necessary
25 behaviours. There are _no_ behaviours that Widgets are obliged to
26 provide: you can make a doesn't-do-anything-at-all widget if you like:
28 mkws.registerWidgetType('Sluggard', function() {});
30 More commonly, widgets will subscribe to one or more events, so that
31 they're notified when something interesting happens. For example, the
32 `Log` widget asks to be notified when a `log` event happens, and
33 appends the logged message to its node, as follows:
35 mkws.registerWidgetType('Log', function() {
38 this.team.queue("log").subscribe(function(teamName, timestamp, message) {
39 $(that.node).append(teamName + ": " + timestamp + message + "<br/>");
43 This simple widget illustrates several important points:
45 * The base widget object (`this`) has several baked-in properties and
46 methods that are available to individual widgets. These include
47 `this.team` (the team that this widget is a part of) and `this.node`
48 (the DOM element of the widget). See below for a full list.
50 * The team object (`this.team`) also has baked-in properties and
51 methods. These include the `queue` function, which takes an event-name
52 as its argument. See below for a full list.
54 * You can add functionality to a widget by subscribing it to an
55 event's queue using `this.team.queue("EVENT").subscribe`. The
56 argument is a function which is called whenever the event is
57 published. The arguments to the function are different for different
60 * As with so much JavaScript programming, the value of the special
61 variable `this` is lost inside the `subscribez` callback function,
62 so it must be saved if it's to be used inside that callback
63 (typically as a local variable named `that`).
66 Widget specialisation (inheritance)
67 -----------------------------------
69 Many widgets are simple specialisations of existing widgets. For
70 example, the `Record` widget is the same as the `Records` widget
71 except that it defaults to displaying a single record. It's defined as
74 mkws.registerWidgetType('Record', function() {
75 mkws.promotionFunction('Records').call(this);
76 if (!this.config.maxrecs) this.config.maxrecs = 1;
79 Remember that when a promotion function is called, it's passed a base
80 widget object that's not specialised for any particular task. To make
81 a specialised widget, you first promote that base widget into the type
82 that you want to specialise from -- in this case, `Records` -- using
83 the promotion function that's been registered for that type.
85 Once this has been done, the specialisations can be introduced. In
86 this case, it's a very simple matter of changing the `maxrecs`
87 configuration setting to 1 unless it's already been given an explicit
88 value. (That would occur if the HTML used an element like `<div
89 class="mkwsRecord" maxrecs="2">`, though it's not obvious why anyone
97 Widget properties and methods
98 -----------------------------
100 The following properties and methods exist in the bare widget object
101 that is passed into `registerWidgetType`'s callback function, and can
102 be used by the derived widget.
104 * `String this.type` --
105 A string containing the type of the widget.
107 * `Team this.team` --
108 The team object to which this widget belongs. The team has
109 several additional important properties and methods, described
112 * `DOMElement this.node` --
113 The DOM element of the widget
115 * `Hash this.config` --
116 A table of configuration values for the widget. This table
117 inherits missing values from the team's configuration, which
118 in turn inherits from the top-level MKWS configuration, which
119 inherits from the default configuration. Instances of widgets
120 in HTML can set configuration items as HTML attributes: for
121 example, the HTML element
122 `<div class="mkwsRecords" maxrecs="10">`.
123 creates a widget for which `this.config.maxrecs` is set to 10.
125 * `String this.toString()` --
126 A function returning a string that briefly names this
127 widget. Can be useful in logging.
129 * `Void this.log(string)` --
130 A function to log a string for debugging purposes. The string
131 is written on the browser console, and also published to any
132 subcribers to the `log` event.
134 * `String this.value()` --
135 A function returning the value of the widget's HTML element.
141 Since the team object is supposed to be opaque to widgets, all access
142 is via the following API methods rather than direct access to
145 * `String team.name()`
146 * `Bool team.submitted()`
147 * `Num team.perpage()`
148 * `Num team.totalRecordCount()`
149 * `Num team.currentPage();`
150 * `String team.currentRecordId()`
151 * `String team.currentRecordData()` --
152 Simple accessor functions that provide the ability to read
153 properties of the team.
155 * `Array team.filters()` --
156 Another accessor function, providing access to the array of
157 prevailing filters (which narrow the search results by means
158 of Pazpar2 filters and limits). This is really too complicated
159 an object for the widgets to be given access to, but it's
160 convenient to do it this way. If you must insist on using
161 this, see the `Navi` widget, which is the only place it's used.
163 * `Hash team.config()` --
164 Access to the team's configuration settings. There is almost
165 certainly no reason to use this: the settings that haven't
166 been overridden are accessible via `this.config`.
168 * `Void team.set_sortOrder(string)`
169 * `Void team.set_perpage(number)` --
170 "Setter" functions for the team's sortOrder and perpage
171 functions. Unlikely to be needed outside of the `Sort` and
174 * `Queue team.queue(eventName)` --
175 Returns the queue associated with the named event: this can be
176 used to subscribe to the event (or more rarely to publish it).
178 * `Bool team.targetFiltered(targetId)` --
179 Indicates whether the specified target has been filtered by
180 selection as a facet.
182 * `Void team.newSearch(query, sortOrder, maxrecs, perpage, limit, targets, targetfilter)` --
183 Starts a new search with the specified parameters. All but the
184 query may be omitted, in which case the prevailing defaults
187 * `Void team.reShow()` --
188 Using the existing search, re-shows the result records after a
189 change in sort-order, per-page count, etc.
191 * `String team.recordElementId(recordId)` --
192 Utility function for converting a record identifer (returned
193 from Pazpar2) into a version suitable for use as an HTML
196 * `String team.renderDetails(recordData)` --
197 Utility function returns an HTML rendering of the record
198 represented by the specified data.
200 * `Template team.loadTemplate(templateName)` --
201 Loads (or retrieves from cache) the named Handlebars template,
202 and returns it in a form that can be invoked as a function,
205 Some of these methods either (A) are really too low-level and should
206 not be exposed, or (B) should be widget-level methods. The present
207 infelicities reflect the fact that some code that rightly belongs in
208 widgets is still in the team. When we finish migrating it, the widget
209 API should get simpler.
213 Copyright (C) 2013-2014 by IndexData ApS, <http://www.indexdata.com>