Inheritance patterns

From one, many From many, oneClass inheritance and composition patterns in YUI Luke Smith

It’s war

Being a web developer is hard. We got it.

Development time VSMaintenance time

Development time

Development time • Prototyping • Structuring

• Prototyping• Structuring

ad er★L o nd G rids S Re set a★ CS ★ Module system ★ Custom Event system

Class structure strategies • Pseudo-classical • Prototypal • Augmentation (Class A + Class B) • Plugins • Class extensions (mixins) • MVC

Class structure strategies • Pseudo-classical • Prototypal • Augmentation • Plugins • Class extensions • MVC

Class structure strategies • Pseudo-classical Native Pseudo-classical • Prototypal • Prototypal • Augmentation • Plugins Artiﬁcial • Class extensions • MVC

Class structure strategies • Pseudo-classical Native • Prototypal

Pseudo-classical (Old school)

Pseudo-classicalfunction SubClass() { // constructor}SubClass.prototype = new SuperClass();SubClass.prototype.someProperty = "booga!";SubClass.prototype.someMethod = function () { ... };...SubClass.someStaticMethod = function () { ... };...

Pseudo-classicalY.extend = function (SubClass, SuperClass, proto, static)function SubClass() { // constructor}SubClass.prototype = new SuperClass();SubClass.prototype.someProperty = "booga!";SubClass.prototype.someMethod = function () { ... };...SubClass.someStaticMethod = function () { ... };...

Pseudo-classicalY.extend = function (SubClass, SuperClass, proto, static)function SubClass() { // constructor}Y.extend(SubClass, SuperClass);SubClass.prototype.someProperty = "booga!";SubClass.prototype.someMethod = function () { ... };...SubClass.someStaticMethod = function () { ... };...

Pseudo-classicalY.extend = function (SubClass, SuperClass, proto, static)function SubClass() { // constructor}Y.extend(SubClass, SuperClass, { someProperty: "booga!", someMethod : function () { ... }, ...});SubClass.someStaticMethod = function () { ... };...

Pseudo-classicalY.extend = function (SubClass, SuperClass, proto, static)function SubClass() { // constructor}Y.extend(SubClass, SuperClass, { someProperty: "booga!", someMethod : function () { ... }, ...}, { someStaticMethod: function () { ... }, ...});

Pseudo-classicalY.extend = function (SubClass, SuperClass, proto, static)Y.SubClass = Y.extend( function() { // constructor }, /* extends */ SuperClass, { // Instance members someProperty: "booga!", someMethod : function () { ... } }, { // Static members someStaticMethod: function () { ... } });

Y.extend() PROs• Creates a “clean” subclass relationship• no YUI class requirement• Preserves instanceof• SubClass.superclass (not super, but close)• Control superclass constructor execution

Y.extend() CONs• No multiple inheritance• Manual constructor chaining required• Constructor chaining is awkward• Constructor chaining may be costly

Y.extend() CONs• No multiple inheritance• Manual constructor chaining required• Constructor chaining is awkward• Constructor chaining may be costly function SubClass() { // Chain superclass constructor SubClass.superclass.constructor.apply(this, arguments); // My constructor stuff ... }

Y.extend() CONs• No multiple inheritance• Manual constructor chaining required• Constructor chaining is awkward• Constructor chaining may be costly function SubClass() { // Chain superclass constructor SubClass.superclass.constructor.apply(this, arguments); A RD W KW // My constructor stuff A ... }

Y.extend() CONs• No multiple inheritance• Manual constructor chaining required• Constructor chaining is awkward• Constructor chaining may be costly function SubClass() { // Chain superclass constructor SubClass.superclass.constructor.apply(this, arguments); A RD W KW COST // My constructor stuff A LY? ... }

To sum up• Good for basic class inheritance• If you can extend Y.Base, there are more options

Prototypal

PrototypalY.extend = function(SubClass, SuperClass,...) { var superProto = SuperClass.prototype, subProto = Y.Object(superProto); SubClass.prototype = subProto; ...

PrototypalY.Object = (function () { function F() {} return function (obj) { F.prototype = obj; return new F(); };})();

Prototypal // Old and busted SubClass.prototype = new SuperClass(); SuperClass SubClassf(n) f(n) Constructor Constructor{} {} Prototype Prototype

Prototypal // Old and busted SubClass.prototype = new SuperClass(); BA SuperClass D SubClassf(n) f(n) Constructor Constructor{} {} Prototype Prototype

Prototypal // Old and busted SubClass.prototype = new SuperClass(); SuperClass SubClassf(n) f(n) Constructor Constructor{} {} Prototype Prototype

Prototypal Y.Object = (function () { function F() {} return function (obj) { F.prototype = obj; return new F(); }; })(); SuperClass (anon) SubClassf(n) f(n) f(n) EMPTY Constructor Constructor Constructor{} {} {} Prototype Prototype Prototype

PrototypalY.Object = (function () { function F() {} return function (obj) { F.prototype = obj; return new F(); };})(); (anon) f(n) EMPTY Constructor{} {} Any Object Prototype

PrototypalY.Object = (function () { function F() {} return function (obj) { F.prototype = obj; return new F(); };})(); (anon) f(n) EMPTY Constructor{} {} f(n) (anon) EMPTY Constructor Any Object Prototype New Object {} Prototype

Factory constructorfunction Set() { var that = (this instanceof Set) ? this : Y.Object(Set.prototype); // use that instead of this [].push.apply(that._items, arguments); return that;}

Factory constructorfunction Set() { var that = (this instanceof Set) ? this : Y.Object(Set.prototype); // use that instead of this [].push.apply(that._items, arguments); return that;}var set = new Set(‘a’,’b’);

Factory constructorfunction Set() { var that = (this instanceof Set) ? this : Y.Object(Set.prototype); // use that instead of this [].push.apply(that._items, arguments); return that;}var set = new Set(‘a’,’b’);set instanceof Set; // true

Factory constructorfunction Set() { var that = (this instanceof Set) ? this : Y.Object(Set.prototype); // use that instead of this [].push.apply(that._items, arguments); return that;}var set = Set(‘a’,’b’); // <-- OOPS! I forgot new!

Factory constructorfunction Set() { var that = (this instanceof Set) ? this : Y.Object(Set.prototype); // use that instead of this [].push.apply(that._items, arguments); return that;}var set = Set(‘a’,’b’);set instanceof Set; // true

Y.Object() PROs• Avoids copying a lot of properties• Can be used to make factory constructors• Can be used to store original values for revert• Any object can be the prototype• Avoids class explosion

Y.Object() CONs• No multiple inheritance• Factory constructor can promote sloppiness• Can’t use hasOwnProperty in for/in loops

To sum up• Useful for some internal logic patterns• Not a good fit for most web app problems• Common use suggests need for a constructor

To sum up• Useful for some internal logic patterns• Not a good fit for most web app problems• Common use suggests need for a constructor var account1 = Y.Object(accountProto); account1.id = 1234; account1.holder = John Q. Consumer; var account2 = Y.Object(accountProto); account2.id = 1235; account2.holder = Jane B. Investor;

To sum up• Useful for some internal logic patterns• Not a good fit for most web app problems• Common use suggests need for a constructor var account1 = Y.Object(accountProto); CO account1.id = 1234; NS account1.holder = John Q. Consumer; TR UC var account2 = Y.Object(accountProto); TO account2.id = 1235; R account2.holder = Jane B. Investor;

To sum up• Useful for some internal logic patterns• Not a good fit for most web app problems• Common use suggests need for a constructor function Account(id, holder) { this.id = id; this.holder = holder; } var account1 = new Account(1234, John Q. Consumer); var account2 = new Account(1235, Jane B. Invester);

Class structure strategies ✓ Pseudo-classical Native ✓ Prototypal • Augmentation • Plugins Artiﬁcial • Class extensions • MVC

instanceof

Augmentation B A C

AugmentationY.augment = function (to, from, force, whitelist, config)Y.ModelList = Y.extend( function () { /* constructor */ ModeList.superclass.constructor.apply(this, arguments); }, Y.Base, { /* prototype */ }, { /* static */ });Y.augment(Y.ModelList, Y.ArrayList);

AugmentationY.augment(Y.ModelList, Y.ArrayList);var list = new Y.ModelList({ ... });list.each(function (item) { ... }); ModelList Constructor ArrayList Prototype Constructor create init Prototype each item

AugmentationY.augment(Y.ModelList, Y.ArrayList); augmentvar list = new Y.ModelList({ ... });list.each(function (item) { ... }); ModelList Constructor ArrayList Prototype Constructor create init Prototype each each item item

AugmentationY.augment(Y.ModelList, Y.ArrayList);var list = new Y.ModelList({ ... });list.each(function (item) { ... }); ModelList Constructor ArrayList Prototype Constructor create init Prototype each each item item

AugmentationY.augment(Y.ModelList, Y.ArrayList);var list = new Y.ModelList({ ... });list.each(function (item) { ... }); ModelList Constructor ArrayList list Prototype Prototype Constructor create create init Prototype ModelList Constructor Prototype create init init each item each each each item item item

AugmentationY.augment(Y.ModelList, Y.ArrayList);var list = new Y.ModelList({ ... });list.each(function (item) { ... }); ModelList Constructor ArrayList list Prototype Constructor create init Prototype ModelList Constructor Prototype create init each item each each item item Prototype

AugmentationY.augment(Y.ModelList, Y.ArrayList);var list = new Y.ModelList({ ... });list.each(function (item) { ... }); ModelList Constructor ArrayList list Prototype Constructor create init Prototype each each item item Prototype

AugmentationY.augment(Y.ModelList, Y.ArrayList);var list = new Y.ModelList({ ... }); eachlist.each(function (item) { ... }); ModelList Constructor ArrayList list Prototype Constructor create init Prototype each each item item Prototype

AugmentationY.augment(Y.ModelList, Y.ArrayList);var list = new Y.ModelList({ ... }); eachlist.each(function (item) { ... }); ModelList Constructor ArrayList list Prototype each create Constructor 1. Copy item init Prototype each each item item Prototype

AugmentationY.augment(Y.ModelList, Y.ArrayList);var list = new Y.ModelList({ ... }); eachlist.each(function (item) { ... }); ModelList Constructor ArrayList list Prototype each create Constructor 1. Copy item init Prototype 2. Construct each each item item Prototype

AugmentationY.augment(Y.ModelList, Y.ArrayList);var list = new Y.ModelList({ ... });list.each(function (item) { ... }); ModelList Constructor ArrayList list Prototype each create Constructor 1. Copy item init Prototype 2. Construct each each 3. Execute item item Prototype

AugmentationY.augment = function (to, from, force, whitelist, config)Y.augment(Y.HistoryBase, Y.EventTarget, null, null, { emitFacade : true, prefix : history, preventable: false, queueable : true});

Y.augment() PROs• Defers constructor overhead• Can augment with multiple classes• Supports class or instance augmentation• No YUI class requirement

Y.augment() CONs• First augmented method call is costly• instanceof is false for augmenting classes• Consumes more memory• Limited control of constructor invocation

To sum up• Use it to simulate lazy multiple inheritance• Y.Base-based classes should use class extensions• Beware the diamond problem• Weigh the importance of constructor deferral

To sum up• Use it to simulate lazy multiple inheritance• Y.Base-based classes should use class extensions• Beware the diamond problem• Weigh the importance of constructor deferral Y.SubClass = Y.extend( function () { Y.SuperClass.apply(this, arguments); Y.EventTarget.apply(this, { /* config */ }); }, Y.SuperClass, // <-- one "official" extention class Y.mix({ /* prototype */ }, Y.EventTarget.prototype), { /* static */ });

PluginsA a a a a

Plugins var overlay = new Y.Overlay({ ... }); overlay.plug(Y.Plugin.Drag); overlay.dd.set(lock, true); overlay.unplug(dd);

Plugins var overlay = new Y.Overlay({ ... }); overlay.plug(Y.Plugin.Drag); overlay.dd.set(lock, true); overlay.unplug(dd); Overlay Constructor Attributes x y

Plugins var overlay = new Y.Overlay({ ... }); overlay.plug(Y.Plugin.Drag); overlay.dd.set(lock, true); overlay.unplug(dd); Overlay overlay Constructor Attributes Attributes x x y y

Plugins var overlay = new Y.Overlay({ ... }); overlay.plug(Y.Plugin.Drag); overlay.dd.set(lock, true); overlay.unplug(dd); Overlay Constructor overlay Plugin.Drag Constructor ATTRS Attributes x x ATTRS y y lock

Plugins var overlay = new Y.Overlay({ ... }); overlay.plug(Y.Plugin.Drag); overlay.dd.set(lock, true); overlay.unplug(dd); Overlay Constructor overlay overlay.dd Plugin.Drag Attributes Constructor Attributes lock ATTRS x x ATTRS y y lock

Plugins var overlay = new Y.Overlay({ ... }); overlay.plug(Y.Plugin.Drag); overlay.dd.set(lock, true); overlay.unplug(dd); Overlay Constructor overlay overlay.dd Plugin.Drag dd Attributes Constructor Attributes lock ATTRS x x ATTRS y y lock

Plugins var overlay = new Y.Overlay({ ... }); overlay.plug(Y.Plugin.Drag); overlay.dd.set(lock, true); overlay.unplug(dd); Overlay Constructor overlay Plugin.Drag Constructor ATTRS Attributes x x ATTRS y y lock

The requirementsHost class • Y.Plugin.Host (free in Y.Base, or add with Y.augment)Plugin class • Static NS property

The requirementsHost class • Y.Plugin.Host (free in Y.Base, or add with Y.augment)Plugin class • Static NS property That’s it

Plugins (instance) Y.Plugin.Host.prototype.plug = function (Plugin, config) { ... if (Plugin && Plugin.NS) { config.host = this; this[Plugin.NS] = new Plugin(config); } };

Plugins (instance) Y.Plugin.Host.prototype.plug = function (Plugin, config) { ... if (Plugin && Plugin.NS) { config.host = this; this[Plugin.NS] = new Plugin(config); } }; overlay.dd.set(lock, true); overlay.unplug(dd);

The contractSHOULD✓ Expect an object constructor argument with ‘host’ property

The contractSHOULD MAY✓ Expect an object ✓ Provide namespaced API constructor argument ✓ Modify core behavior via with ‘host’ property events or AOP

The contractSHOULD MAY✓ Expect an object ✓ Provide namespaced API constructor argument ✓ Modify core behavior via with ‘host’ property events or AOPMUST✓ Remove all traces when unplugged

The contractSHOULD MAY✓ Expect an object ✓ Provide namespaced API constructor argument ✓ Modify core behavior via with ‘host’ property events or AOPMUST MUST NOT✓ Remove all traces ✓ Modify host directly when unplugged other than add the namespace

Plugins (class) Y.Plugin.Host.plug(Y.Overlay, Y.Plugin.Drag, { handles: [.yui3-widget-hd] }); var overlay = new Y.Overlay({ ... }); overlay.dd.set(lock, true);

Plugin PROs• Avoids method/property naming collisions• Preserves host behavior when unplug()ed• Plug classes or instances• Generic plugins can work for multiple host types• Works on Nodes

Plugin CONs• Fragments API• Plugin contract to restore host can add code weight• Difficult to manage competing plugins• plug() could use a little sugar

to sum up• Flexible• Better in smaller numbers• Class Plugins vs Augmentation?• Free with Y.Base-based classes and Y.Nodes (have I mentioned that you should use Y.Base?)

Class Extensions B Y.Base A C

Class extensionsY.extend = function (SubClass, SuperClass, proto, static)Y.SubClass = Y.extend( function() { SubClass.superclass.constructor.apply(this, arguments); }, /* extends */ Y.Base { someProperty: ‘booga!’, someMethod : function () { ... } }, { NAME: ‘subsub’, /* NAME */ ‘subsub’, ATTRS: { ... } });

Class extensionsY.extend = function (SubClass, SuperClass, proto, static)Y.SubClass = Y.extend( NAME: ‘subsub’, /* NAME */ ‘subsub’, /* extends */ Y.Base { someProperty: ‘booga!’, someMethod : function () { ... } }, { ATTRS: { ... } });

Class extensionsY.extend = function (SubClass, SuperClass, proto, static)Y.SubClass = Y.extend( NAME: ‘subsub’, /* NAME */ ‘subsub’, /* extends */ Y.Base [], // <-- class extensions! { someProperty: ‘booga!’, someMethod : function () { ... } }, { ATTRS: { ... } });

Class extensionsY.Base.create = function(NAME, SuperClass, ext, proto, static)Y.SubClass = Y.extend( NAME: ‘subsub’, /* NAME */ ‘subsub’, /* extends */ Y.Base [], // <-- class extensions! { someProperty: ‘booga!’, someMethod : function () { ... } }, { ATTRS: { ... } });

Class extensionsY.Base.create = function(NAME, SuperClass, ext, proto, static)Y.LineSeries = Y.Base.create(lineSeries, Y.CartesianSeries, [ Y.Lines ], { /* Glue Y.Lines APIs to Y.CartesianSeries APIs */ });

Class extensionsY.Base.create = function(NAME, SuperClass, ext, proto, static)Y.LineSeries = Y.Base.create(lineSeries, Y.CartesianSeries, [ Y.Lines ], { /* Glue Y.Lines APIs to Y.CartesianSeries APIs */ });Y.ComboSeries = Y.Base.create(comboSeries, Y.CartesianSeries, [ Y.Fills, Y.Lines, Y.Plots ], { /* Glue Y.Fills etc APIs to Y.CartesianSeries APIs */ }, { ATTRS: { ... } });

Class extensions Y.LineSeries = Y.Base.create(lineSeries, Y.CartesianSeries, [ Y.Lines ], { ... }); var series = new Y.LineSeries({ ... }); Cartesian LineSeries Lines Constructor Constructor Constructor ATTRS ATTRS Prototype Prototype ATTRS Prototype

Class extensions Y.LineSeries = Y.Base.create(lineSeries, Y.CartesianSeries, [ Y.Lines ], { ... }); var series = new Y.LineSeries({ ... }); Cartesian LineSeries Lines Constructor Constructor Constructor Constructor ATTRS ATTRS Constructor Prototype Prototype ATTRS Prototype

Class extensions Y.LineSeries = Y.Base.create(lineSeries, Y.CartesianSeries, [ Y.Lines ], { ... }); var series = new Y.LineSeries({ ... }); Cartesian LineSeries Lines Constructor Constructor Constructor Constructor Constructor ATTRS ATTRS Constructor Prototype Prototype ATTRS Prototype

Class extensions Y.LineSeries = Y.Base.create(lineSeries, Y.CartesianSeries, [ Y.Lines ], { ... }); var series = new Y.LineSeries({ ... }); Cartesian LineSeries Lines Constructor Constructor Constructor ATTRS ATTRS ATTRS direction type type Prototype Prototype Prototype

Class extensions Y.LineSeries = Y.Base.create(lineSeries, Y.CartesianSeries, [ Y.Lines ], { ... }); var series = new Y.LineSeries({ ... }); Cartesian LineSeries Lines Constructor Constructor Constructor ATTRS ATTRS ATTRS direction styles type type Prototype Prototype Prototype

Class extensions Y.LineSeries = Y.Base.create(lineSeries, Y.CartesianSeries, [ Y.Lines ], { ... }); var series = new Y.LineSeries({ ... }); Cartesian LineSeries Lines Constructor Constructor Constructor ATTRS ATTRS ATTRS direction styles type type direction Prototype type Prototype Prototype

Class extensions Y.LineSeries = Y.Base.create(lineSeries, Y.CartesianSeries, [ Y.Lines ], { ... }); var series = new Y.LineSeries({ ... }); Cartesian LineSeries Lines Constructor Constructor Constructor ATTRS ATTRS ATTRS Prototype Prototype Prototype draw drawLines

Class extensions Y.LineSeries = Y.Base.create(lineSeries, Y.CartesianSeries, [ Y.Lines ], { ... }); var series = new Y.LineSeries({ ... }); Cartesian LineSeries Lines Constructor Constructor Constructor ATTRS ATTRS ATTRS Prototype Prototype Prototype Prototype draw Prototype draw drawLines draw drawLines drawSeries

Class extensions Y.LineSeries = Y.Base.create(lineSeries, Y.CartesianSeries, [ Y.Lines ], { ... }); var series = new Y.LineSeries({ ... }); Cartesian LineSeries Lines Constructor Constructor Constructor ATTRS ATTRS ATTRS Prototype Prototype Prototype draw initializer initializer drawLines initializer initializer initializer initializer

Class extensions Y.LineSeries = Y.Base.create(lineSeries, Y.CartesianSeries, [ Y.Lines ], { ... }); var series = new Y.LineSeries({ ... });1. Constructors are called2. Attributes are set3. initializers are called

Two types of extensions 1. Class decoration Add feature APIs and Attributes 2. Core functionality Satisfy abstract class implementation

Class extensionsY.Base.create = function(NAME, SuperClass, ext, proto, static)Y.Overlay = Y.Base.create(overlay, Y.Widget, [ Y.WidgetStdMod, Y.WidgetPosition, Y.WidgetStack, Y.WidgetPosition, Y.WidgetPositionConstrain]);

Class extensionsY.Base.mix = function(Class, ext)Y.Slider = Y.Base.create(slider, Y.SliderBase, [Y.SliderValueRange]);Y.Base.mix(Y.Slider, [Y.ClickableRail]);

Extensions PROs• Promotes code reuse across environments• Feature APIs are added to the prototype• Can be used to mimic MVC breakdown

Extensions CONs• Requires Y.Base• Initialization overhead• Class definition only (no instance feature additions)• Does not work on Nodes• Increased potential for accidental name collisions

Extension vs Plugin• Extensions can be used to contribute core behavior• Extensions modify the class prototype, plugins are always namespaced• Feature extension constructors are always executed, plugin constructors on plug()• Feature APIs/attributes on the prototype vs class plugins in namespace is a stylistic choice

MVCGo see Eric’s talk tomorrow

There ain’t just one way to do it.

You owe it to future-you to structure your code

Try out plugins and extensions

Invest in the future

Invest in the future (and use Y.Base)

Invest in the future (and use Y.Base) (and join us in #yui)

Thank you Luke Smith @ls_n

http://www.scoop.it	143
http://lanyrd.com	21
http://a0.twimg.com	5
http://webcache.googleusercontent.com	1

Inheritance patterns

by Luke Smith on Nov 03, 2011

Accessibility

Categories

Tags

Upload Details

Usage Rights

4 Embeds 170

Statistics

Inheritance patterns — Presentation Transcript