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.
139 * TODO hideWhenNarrow()
145 In addition to these properties and methods of the bare widget object,
146 some kinds of specific widget add other properties of their own. For
147 example, the `Builder` widget uses a `callback` property as the
148 function that it use to publish the widget definition that it
149 constructs. This defaults to the builtin function `alert`, but can be
150 overridden by derived widgets such as `ConsoleBuilder`.
156 Since the team object is supposed to be opaque to widgets, all access
157 is via the following API methods rather than direct access to
160 * `String team.name()`
161 * `Bool team.submitted()`
162 * `Num team.perpage()`
163 * `Num team.totalRecordCount()`
164 * `Num team.currentPage();`
165 * `String team.currentRecordId()`
166 * `String team.currentRecordData()`
168 These are all simple accessor functions that provide the ability to
169 read properties of the team.
171 * `Array team.filters()` --
172 Another accessor function, providing access to the array of
173 prevailing filters (which narrow the search results by means
174 of Pazpar2 filters and limits). This is really too complicated
175 an object for the widgets to be given access to, but it's
176 convenient to do it this way. If you must insist on using
177 this, see the `Navi` widget, which is the only place it's used.
179 * `Bool team.targetFiltered(targetId)` --
180 Indicates whether the specified target has been filtered by
181 selection as a facet. This is used only by the `Facet` widget,
182 and there is probably no reason for you to use it.
184 * `Hash team.config()` --
185 Access to the team's configuration settings. There is almost
186 certainly no reason to use this: the settings that haven't
187 been overridden are accessible via `this.config`.
189 * `Void team.set_sortOrder(string)`, `Void team.set_perpage(number)` --
190 "Setter" functions for the team's sortOrder and perpage
191 functions. Unlikely to be needed outside of the `Sort` and
194 * `Queue team.queue(eventName)` --
195 Returns the queue associated with the named event: this can be
196 used to subscribe to the event (or more rarely to publish it).
198 * `Void team.newSearch(query, sortOrder, maxrecs, perpage, limit, targets, targetfilter)` --
199 Starts a new search with the specified parameters. All but the
200 query may be omitted, in which case the prevailing defaults
203 * `Void team.reShow()` --
204 Using the existing search, re-shows the result records after a
205 change in sort-order, per-page count, etc.
207 * `String team.recordElementId(recordId)` --
208 Utility function for converting a record identifer (returned
209 from Pazpar2) into a version suitable for use as an HTML
212 * `String team.renderDetails(recordData)` --
213 Utility function returns an HTML rendering of the record
214 represented by the specified data.
216 * `Template team.loadTemplate(templateName)` --
217 Loads (or retrieves from cache) the named Handlebars template,
218 and returns it in a form that can be invoked as a function,
221 Some of these methods either (A) are really too low-level and should
222 not be exposed, or (B) should be widget-level methods. The present
223 infelicities reflect the fact that some code that rightly belongs in
224 widgets is still in the team. When we finish migrating it, the widget
225 API should get simpler.
229 Copyright (C) 2013-2014 by IndexData ApS, <http://www.indexdata.com>