Category: singleton

Implementing Singleton Design Pattern in Apex – Use Case III

This post is part of the series – Design Pattern in ApexToday in this post I will explain how Singleton Design Pattern can be used to call global describe only once.Requirement -When someone inserts an account record, you need to inspect all the fields in the account object.Implementation -Below is the trigger to start with -MyAccountTrigger-AccountHelper -The problem with this approach is that when someone enters huge number of accounts with dataloader, this code will work like -For each insert, it will create a new instance of AccountHelper which in turn will execute GlobalDescribe(). Very soon we will be hit by LimitException.To avoid that, we have to implement Singleton Design Pattern and below are the changes we need to do that -AccountHelper -MyAccountTrigger-Now you can see for a single transaction, we are calling GlobalDescribe only once because we are now not instantiating AccountHelper object for each Account insert, rather we are only instantiating one AccountHelper object per transaction.Hope you understood the usages of Singleton Design Pattern. If you have implemented this design pattern in any other situation, requesting you to share here. Thanks for your feedback....

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Implementing Singleton Design Pattern in Apex – Use Case II

This post is part of the series – Design Pattern in ApexToday in this post I will explain how Singleton Design Pattern can be used to stop calling the same trigger twice.Consider the situation – You as a developer, is updating a field in Trigger which in turns calls a workflow and in that workflow action you are again updating some other field from the same object. And to your surprise, the same trigger is getting triggered again. Getting confused, right?Let’s become more specific with the situation.Consider the below object – Airport__cThe requirements are -Req 1: Send an email if the country and type of an airport changed.Req 2: If the country of an airport changed to “India”, change the type to “International”. To achieve the above two requirements, we have implemented -One trigger, which will send the email if the country and type of an airport changed.One workflow, which will change the type to “International” (Workflow action) if the country of an airport changed to “India”.Here is the trigger -The trigger looks really simple. But you know what will happen, when you will change the country of an airport to “India”, you will get two emails. You know why?First email you will get from Line#6. After that, workflow action will change the type of the airport to “International”. Due to this change you will get another email from Line#11.To solve...

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Implementing Singleton Design Pattern in Apex – Use Case I

This post is part of the series – Design Pattern in ApexSingleton Design Pattern is pretty popular and one of the simplest design pattern available. I will start with the statement from “The Gang of Four” as it describes Singleton Pattern as  –“Ensure a class has only one instance, and provide a global point of access to it.”In this post, I will explain why we need to have Singleton Design Pattern in Apex and how to implement the same.Sometimes it is very much required to have only instances of the class – Logger, Window Manager etc. Typically, these type of objects where only one instance is sufficient to handle the requirements, are called Singleton.With Singleton Design Pattern, you can –Ensure that only one instance of class is getting created.Provide a global point of access to the object.There are many ways to implement Singleton Pattern in apex. Let’s start with few case scenarios:Use Case:Consider the below requirement -Whenever a new account is getting inserted to Salesforce, it should be synced with MDM(Master Data Management) through integration. But if MDM system is down, then Salesforce should not got for synchronization.Let’s start implementing the requirement -Custom Settings – Integration – This will be used to identify whether MDM System is up and running. If MDM System is down, Admin will uncheck the value and then Salesforce will not try for synchronization. Below is how...

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