apex design patterns

Apex Design PatternsDevelopers

Richard Vanhook and Dennis Thong@richardvanhook @denniscfthong

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Richard VanhookSenior Technical Solution Architect@richardvanhook

Dennis ThongDirector - Technical Solution Architect@denniscfthong

The PlanCover four design patterns

▪ Problem▪ Pattern Abstract▪ Code

Your participation is encouraged!

Patterns1. ?2. ?3. ?4. ?

Meet Billy, Your Admin• 3+ yrs as Salesforce Admin• Just recently started coding• Sad because of this:

• Needs your help!

Trigger.AccountTrigger: line 3, column 1System.LimitException: Too many record type describes: 101

The Offending Code

• When a single Account is inserted, what happens?• When 200+ Accounts are inserted…?

trigger AccountTrigger on Account (before insert, before update) { for(Account record : Trigger.new){ AccountFooRecordType rt = new AccountFooRecordType(); .... }}

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public class AccountFooRecordType { public String id {get;private set;} public AccountFooRecordType(){ id = Account.sObjectType.getDescribe() .getRecordTypeInfosByName().get('Foo').getRecordTypeId(); }}

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Solution: Singleton

Singleton

- instance : Singleton

- Singleton()+ getInstance() : Singleton

Let’s Code It!trigger AccountTrigger on Account (before insert, before update) { for(Account record : Trigger.new){ AccountFooRecordType rt = new AccountFooRecordType(); .... }}

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public class AccountFooRecordType { public String id {get;private set;} public AccountFooRecordType(){ id = Account.sObjectType.getDescribe() .getRecordTypeInfosByName().get('Foo').getRecordTypeId(); }}

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• Above is the offending code again• Changes are highlighted in next slides

Let’s Code It!trigger AccountTrigger on Account (before insert, before update) { for(Account record : Trigger.new){ AccountFooRecordType rt = (new AccountFooRecordType()).getInstance(); .... }}

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public class AccountFooRecordType { public String id {get;private set;} public AccountFooRecordType(){ id = Account.sObjectType.getDescribe() .getRecordTypeInfosByName().get('Foo').getRecordTypeId(); } public AccountFooRecordType getInstance(){

return new AccountFooRecordType(); }}

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Let’s Code It!trigger AccountTrigger on Account (before insert, before update) { for(Account record : Trigger.new){ AccountFooRecordType rt = AccountFooRecordType.getInstance(); .... }}

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public class AccountFooRecordType { public String id {get;private set;} public AccountFooRecordType(){ id = Account.sObjectType.getDescribe() .getRecordTypeInfosByName().get('Foo').getRecordTypeId(); } public static AccountFooRecordType getInstance(){

return new AccountFooRecordType(); }}

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Static▪ Can modify member variables, methods, and blocks▪ Executed when?

• When class is introduced (loaded) to runtime environment

▪ How long does that last in Java?• Life of the JVM

▪ In Apex?• Life of the transaction

Let’s Code It!trigger AccountTrigger on Account (before insert, before update) { for(Account record : Trigger.new){ AccountFooRecordType rt = AccountFooRecordType.getInstance(); .... }}

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public class AccountFooRecordType { public String id {get;private set;} public AccountFooRecordType(){ id = Account.sObjectType.getDescribe() .getRecordTypeInfosByName().get('Foo').getRecordTypeId(); } public static AccountFooRecordType getInstance(){

return new AccountFooRecordType(); }}

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Let’s Code It!trigger AccountTrigger on Account (before insert, before update) { for(Account record : Trigger.new){ AccountFooRecordType rt = AccountFooRecordType.getInstance(); .... }}

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public class AccountFooRecordType { public static AccountFooRecordType instance = null; public String id {get;private set;} public AccountFooRecordType(){ id = Account.sObjectType.getDescribe() .getRecordTypeInfosByName().get('Foo').getRecordTypeId(); } public static AccountFooRecordType getInstance(){ if(instance == null) instance = new AccountFooRecordType(); return instance; }}

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Let’s Code It!trigger AccountTrigger on Account (before insert, before update) { for(Account record : Trigger.new){ AccountFooRecordType rt = AccountFooRecordType.getInstance(); .... }}

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public class AccountFooRecordType { private static AccountFooRecordType instance = null; public String id {get;private set;} public AccountFooRecordType(){ id = Account.sObjectType.getDescribe() .getRecordTypeInfosByName().get('Foo').getRecordTypeId(); } public static AccountFooRecordType getInstance(){ if(instance == null) instance = new AccountFooRecordType(); return instance; }}

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Let’s Code It!trigger AccountTrigger on Account (before insert, before update) { for(Account record : Trigger.new){ AccountFooRecordType rt = AccountFooRecordType.getInstance(); .... }}

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public class AccountFooRecordType { private static AccountFooRecordType instance = null; public String id {get;private set;} private AccountFooRecordType(){ id = Account.sObjectType.getDescribe() .getRecordTypeInfosByName().get('Foo').getRecordTypeId(); } public static AccountFooRecordType getInstance(){ if(instance == null) instance = new AccountFooRecordType(); return instance; }}

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Patterns1. Singleton2. ?3. ?4. ?

geocode('moscone center') //=> 37.7845935,-122.3994262

Your Suggestion to Billypublic class GoogleMapsGeocoder{ public static List<Double> getLatLong(String address){ //web service callout of some sort return new List<Double>{0,0}; }}

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But then Billy mentions these requirements▪ Need other options besides Google Maps▪ Allow client code to choose provider

System.debug(GoogleMapsGeocoder.getLatLong('moscone center'));//=> 13:56:36.029 (29225000)|USER_DEBUG|[29]|DEBUG|(0.0, 0.0)

0708

Solution: Strategy

defines a family of algorithms, encapsulates each one, and makes them interchangeable▪ Context => Geocoder▪ operation() => getLatLong()▪ Strategy => GeocodeService▪ ConcreteStrategyA => GoogleMapsImpl▪ ConcreteStrategyB => MapQuestImpl

Context

+operation()

Strategy

+operation()

ConcreteStrategyA

+operation()

Clientstrategies

*1

ConcreteStrategyB

+operation()

Let’s Code Itpublic interface GeocodeService{ List<Double> getLatLong(String address);}

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public class GoogleMapsImpl implements GeocodeService{ public List<Double> getLatLong(String address){ return new List<Double>{0,0}; }}

public class MapQuestImpl implements GeocodeService{ public List<Double> getLatLong(String address){ return new List<Double>{1,1}; }}

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public class Geocoder { private GeocodeService strategy; public Geocoder(GeocodeService s){ strategy = s; } public List<Double> getLatLong(String address){ return strategy.getLatLong(address); }}

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Geocoder geocoder = new Geocoder(new GoogleMapsImpl());System.debug(geocoder.getLatLong('moscone center'));//=> 13:56:36.029 (29225000)|USER_DEBUG|[29]|DEBUG|(0.0, 0.0)

101112

Geocoder

+ Geocoder(GeocodeService)

+getLatLong(String)

GeocodeService

+getLatLong(String)

GoogleMapsImpl

+getLatLong(String)

Clientstrategies

*1

MapQuestImpl

+getLatLong(String)

public class Geocoder { public static final Map<String,Strategy> strategies = new Map<String,Strategy>{'googlemaps' => new GoogleMapsImpl() ,'mapquest' => new MapQuestImpl()}; private GeocodeService strategy; public Geocoder(String name){ strategy = strategies.get(name);} public List<Double> getLatLong(String address){ return strategy.getLatLong(address); }}

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Geocoder geocoder = new Geocoder('googlemaps');System.debug(geocoder.getLatLong('moscone center'));//=> 13:56:36.029 (29225000)|USER_DEBUG|[29]|DEBUG|(0.0, 0.0)

111213

Geocoder

+ Geocoder(String)

+getLatLong(String)

GeocodeService

+getLatLong(String)

GoogleMapsImpl

+getLatLong(String)

Clientstrategies

*1

MapQuestImpl

+getLatLong(String)

public class Geocoder { public class NameException extends Exception{} public static final Map<String,GeocodeService> strategies; static{ GlobalVariable__c gv = GlobalVariable__c.getInstance('strategies'); List<String> strategyNames = new List<String>(); if(gv != null && gv.value__c != null) strategyNames = gv.value__c.split(','); strategies = new Map<String,GeocodeService>(); for(String name : strategyNames){ try{strategies.put(name,(GeocodeService)Type.forName(name+'impl').newInstance());} catch(Exception e){continue;} //skip bad name silently } } private GeocodeService strategy; public Geocoder(String name){ if(!strategies.containsKey(name)) throw new NameException(name); strategy = strategies.get(name); } public List<Double> getLatLong(String address){ return strategy.getLatLong(address); }}

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Patterns1. Singleton2. Strategy3. ?4. ?

Question

Transient selection checkboxes

Calculated Fields with Updates

How do we extend the functionality of an sObject in Apex without adding new fields?

Solution – sObject Decorator

(aka Wrapper Classes v2.0)

Example - ScenarioWeather sObject

▪ City__c▪ TempInFahrenheit__c (in Fahrenheit)

VisualForce Requirements▪ Stored temperature in Fahrenheit is displayed in Celcius▪ User enters Temperature in Celcius and is stored to the record in Fahrenheit

Bi-directional Display and Calculation

The Code – Decorated sObject Classpublic class DecoratedWeather {

public Weather__c weather { get; private set; }

public DecoratedWeather ( Weather__c weather) { this.weather = weather;

}

public Decimal tempInCelcius { get {

if (weather != null && tempInCelcius == null )tempInCelcius = new Temperature().FtoC(weather.TempInFahrenheit__c);

return tempInCelcius;

} set {

if (weather != null && value != null ) weather.TempInFahrenheit__c= new Temperature().CtoF(value);

tempInCelcius = value;}

}}

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The Code – Custom Controllerpublic class Weather_Controller {

public List<DecoratedWeather> listOfWeather {

get { if (listOfWeather == null) {

listOfWeather = new List<DecoratedWeather>(); for (Weather__c weather : [select name, temperature__c from Weather__c]) {

listOfWeather.add(new DecoratedWeather(weather)); }

} return listOfWeather;

} private set;

}}

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The Code – VisualForce Page<apex:page controller="weather_controller">

<!-- VF page to render the weather records with Ajax that only rerenders the page on change of the temperature

--> <apex:form id="theForm"> <apex:pageBlock id="pageBlock"> <apex:pageBlockTable value="{!listOfWeather}" var="weather"> <apex:column value="{!weather.weather.name}"/> <apex:column headerValue="Temperature (C)"> <apex:actionRegion > <apex:inputText value="{!weather.tempInCelcius}"> <apex:actionSupport event="onchange" reRender="pageBlock"/> </apex:inputText> </apex:actionRegion> </apex:column> <apex:column headerValue="Temperature (F)" value="{!weather.weather.Temperature__c}" id="tempInF"/> </apex:pageBlockTable>

</apex:pageBlock> </apex:form></apex:page>

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logic!!!

Finally, on the VisualForce page

Patterns1. Singleton2. Strategy3. sObject Decorator4. ?

Billy Has a New Problem!Billy wrote a trigger to create an order on close of an opportunity,

however:▪ It always creates a new order every time the closed opportunity is

updated▪ When loading via Data Loader, not all closed opportunities result in an

order

The Offending Codetrigger OpptyTrigger on Opportunity (after insert, after update) {

if (trigger.new[0].isClosed) {Order__c order = new Order__c();…insert order

}}

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No Bulk Handling

Occurs regardless of prior state

Poor reusability

Any Better?trigger OpptyTrigger on Opportunity (after insert, after update) {

new OrderClass().CreateOrder(trigger.new);

}

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public class OrderClass {

public void CreateOrder(List<Opportunity> opptyList) {for (Opportunity oppty : opptyList) {

if (oppty.isClosed) {Order__c order = new Order__c();...insert order;

}}

}}

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Occurs regardless of prior state

Not bulkified

How’s this?trigger OpptyTrigger on Opportunity (before insert, before update) {

if (trigger.isInsert) {new OrderClass().CreateOrder(trigger.newMap, null);

elsenew OrderClass().CreateOrder(trigger.newMap, trigger.oldMap);

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public class OrderClass {

public void CreateOrder(Map<Opportunity> opptyMapNewMap<Opportunity> opptyMapOld) {

List<Order__c> orderList = new List<Order__c>();for (Opportunity oppty : opptyMapNew.values()) {

if (oppty.isClosed && (opptyMapOld == null ||!opptyMapOld.get(oppty.id).isClosed)) {

Order__c order = new Order__c();...orderList.add(order);

}}insert orderList ;

}

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This code is highly coupled and not reusable

At least it’s bulkified

Solution – Bulk Transition

• Checks for eligible records that have changed state and match criteria

• Calls utility class method to perform the work

• Only eligible records are passed in

• Generic utility class method that can be called from any context

At Last!!!trigger OpptyTrigger on Opportunity (after insert, after update) {

if (trigger.isAfter && (trigger.isInsert || trigger.isUpdate)) {List<Opportunity> closedOpptyList = new List<Opportunity>();for (Opportunity oppty : trigger.new) {

if (oppty.isClosed && (trigger.isInsert || (trigger.isUpdate &&!trigger.oldMap.get(oppty.id).isClosed)))

closedOpptyList.add(oppty);}if (!closedOpptyList.isEmpty())

new OrderClass().CreateOrderFromOpptys(closedOpptyList)

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public class OrderClass {public void CreateOrdersFromOpptys(List<Opportunity> opptyList) {

List<Order__c> orderList = new List<Order__c>();for (Opportunity oppty : opptyList) {

Order__c order = new Order__c();...orderList.add(order);

}insert orderList ;

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Trigger handles state transition

This method is now a lot more reusable and is bulk-

safe

Patterns1. Singleton2. Strategy3. sObject Decorator4. Bulk State Transition

ResourcesWrapper Classes - http://wiki.developerforce.com/page/Wrapper_Class Apex Code Best Practices - http://wiki.developerforce.com/page/Apex_Code_Best_Practices Apex Web Services and Callouts - http://wiki.developerforce.com/page/Apex_Web_Services_and_Callouts Sample Code - https://github.com/richardvanhook/Force.com-Patterns

More at #DF13Apex Enterprise Patterns: Building Strong FoundationsTuesday, November 19th: 12:15 pm - 01:00 pm - Moscone Center West – 2009High Reliability DML and Concurrency Design Patterns for ApexMonday, November 18th: 11:15 am - 12:00 pm - Moscone Center West – 2009Making Your Apex and Visualforce ReusableTuesday, November 19th: 12:15 pm - 01:00 pm - Moscone Center West – 2022Design Patterns for Asynchronous ApexTuesday, November 19th: 05:15 pm - 06:00 pm - Moscone Center West – 2024The Apex Ten CommandmentsWednesday, November 20th: 04:00 pm - 04:45 pm - Moscone Center West - 2006 / 2008

Speaker Name

Dennis Thong,@denniscfthong

Speaker Name

Richard Vanhook,@richardvanhook

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