4 Development with MKWS consists primarily of defining new types of
5 widgets. These can interact with the core functionality is several
8 You create a new widget type by calling the mkws.registerWidgetType
9 function, passing in the widget name and a function. The name is used
10 to recognise HTML elements as being widgets of this type -- for
11 example, if you register a "Foo" widget, elements like <div
12 class="mkwsFoo"> will be widgets of this type.
14 The function promotes a bare widget object (passed as `this') into a
15 widget of the appropriate type. MKWS doesn't use classes or explicit
16 prototypes: it just makes objects that have the necessary
17 behaviours. Widgets have *no* behaviours that they have to provide:
18 you can make a doesn't-do-anything-at-all widget if you like:
20 mkws.registerWidgetType('Sluggard', function() {});
22 More commonly, widgets will subscribe to one or more events, so that
23 they're notified when something interesting happens. For example, the
24 "Log" widget asks to be notified when a "log" event happens, and
25 appends the logged message to its node, as follows:
27 mkws.registerWidgetType('Log', function() {
30 this.team.queue("log").subscribe(function(teamName, timestamp, message) {
31 $(that.node).append(teamName + ": " + timestamp + message + "<br/>");
35 This simple widget illustrates several important points:
37 * The base widget object (`this') has several baked-in properties and
38 methods that are available to individual widgets. These include
39 this.team (the team that this widget is a part of) and this.node
40 (the DOM element of the widget).
42 * The team object (`this.team') also has baked-in properties and
43 methods. These include the queue function, which takes an event-name
44 as its argument. It's possible to subscribe to an event's queue
45 using this.team.queue("EVENT").subscribe. The argument is a function
46 which is called whenever the event is published. The arguments to
47 the function are different for different events.
49 * The value of `this' is lost inside the subscribe callback, so it
50 must be saved if it's to be used inside that callback (typically as
51 a local variable named `that').
54 SPECIALISATION (INHERITANCE)
55 ============================
57 Many widgets are simple specialisations of existing widgets. For
58 example, the "Record" widget is the same as the "Records" widget
59 except that it defaults to displaying a single record. It's defined as
62 mkws.registerWidgetType('Record', function() {
63 mkws.promotionFunction('Records').call(this);
64 if (!this.config.maxrecs) this.config.maxrecs = 1;
67 Remember that when a promotion function is called, it's passed a base
68 widget object that's not specialised for any particular task. To make
69 a specialised widget, first promote that base widget into the type
70 that you want to specialise from -- in this case, "Records" -- using
71 the promotion function that's been registered for that type.
73 Once this has been done, the specialisations can be introduced. In
74 this case, it's a very simple matter of changing the "maxrecs"
75 configuration setting to 1 unless it's already been given an explicit
76 value. (That would occur if the HTML used an element like <div
77 class="mkwsRecord" maxrecs="2">, though it's not obvious why anyone
81 WIDGET PROPERTIES AND METHODS
82 =============================
85 A string containing the type of the widget.
88 The team object to which this widget belongs. The team has
89 several additional important properties and methods, described
93 The DOM element of the widget
96 A table of configuration values for the widget. This table
97 inherits missing values from the team's configuration, which
98 in turn inherits from the top-level MKWS configuration, which
99 inherits from the default configuration. Instances of widgets
100 in HTML can set configuration items as HTML attributes, as in
101 <div class="mkwsRecords" maxrecs="2">.
103 String this.toString()
104 A function returning a string that briefly names this
105 widget. Can be useful in logging.
107 Void this.log(string)
108 A function to log a string for debugging purposes. The string
109 is written on the browser console, and also published to any
113 A function returning the value of the widget's HTML element.
119 Since the team object is supposed to be opaque to widgets, all access
120 is via the following API methods rather than direct access to
124 Bool team.submitted()
126 Num team.totalRecordCount()
127 Num team.currentPage();
128 String team.currentRecordId()
129 String team.currentRecordData()
130 Simple accessor functions that provide the ability to read
131 properties of the team.
134 Another accessor function, providing access to the array of
135 prevailing filters (which narrow the search results by means
136 of Pazpar2 filters and limits). This is really too complicated
137 an object for the widgets to be given access to, but it's
138 convenient to do it this way. See the "Navi" widget, which is
139 the only place it's used.
142 Access to the team's configuration settings. There is almost
143 certainly no reason to use this: the settings that haven't
144 been overridden are accessible via this.config.
146 Void team.set_sortOrder(string)
147 Void team.set_perpage(number)
148 "Setter" functions for the team's sortOrder and perpage
149 functions. Unlikely to be needed outside of the "Sort" and
152 Queue team.queue(eventName)
153 Returns the queue associated with the named event: this can be
154 used to subscribe to the event (or more rarely to publish it).
156 Bool team.targetFiltered(targetId)
157 Indicates whether the specified target has been filtered by
158 selection as a facet.
160 Void team.newSearch(query, sortOrder, maxrecs, perpage, limit, targets, targetfilter)
161 Starts a new search with the specified parameters. All but the
162 query may be omitted, in which case the prevailing defaults
166 Using the existing search, re-shows the result records after a
167 change in sort-order, per-page count, etc.
169 String team.recordElementId(recordId)
170 Utility function for converting a record identifer (returned
171 from Pazpar2) into a version suitable for use as an HTML
174 String team.renderDetails(recordData)
175 Utility function returns an HTML rendering of the record
176 represented by the specified data.
178 Template team.loadTemplate(templateName)
179 Loads (or retrieves from cache) the named Handlebars template,
180 and returns it in a form that can be invoked as a function,
183 Some of these methods either (A) are really too low-level and should
184 not be exposed, or (B) should be widget-level methods. The present
185 infelicities reflect the fact that some code that rightly belongs in
186 widgets is still in the team. When we finish migrating it, the widget
187 API should get simpler.