{"id":5446,"date":"2022-01-06T04:35:11","date_gmt":"2022-01-06T04:35:11","guid":{"rendered":"https:\/\/studysection.com\/blog\/?p=5446"},"modified":"2022-01-06T06:26:24","modified_gmt":"2022-01-06T06:26:24","slug":"apex-design-patterns-singleton","status":"publish","type":"post","link":"https:\/\/studysection.com\/blog\/apex-design-patterns-singleton\/","title":{"rendered":"Apex Design Patterns – Singleton"},"content":{"rendered":"

Introduction<\/h2>\n

While implementing any code<\/a>, sometimes we need to create an object of a class but we want to initiate it only once means we initiate an object once for the lifetime of its execution context.<\/p>\n

Why do we need the singleton pattern?<\/h3>\n
    \n
  1. Singleton pattern unable us to use the facility of global variables. Since apex does not support global variables but with the help of a singleton pattern, we can achieve it.<\/li>\n
  2. Singleton patterns also help us to govern the apex limits because we are not executing the same code again and again.<\/li>\n<\/ol>\n

    Problem<\/strong>
    \nSometimes a developer writes code that needs to initiate an object of a class again and again in a loop. It will result in inefficient, low-performing code, as well as the potential for governor limitations to be exceeded.<\/p>\n

    For example:<\/em><\/strong>
    \nPublic class Abc{
    \n\tfor(Account eachRecord : [SELECT Id, Name FROM Account]){
    \n\tXyz obj = new Xyz();
    \n}
    \n}
    \nPublic class Xyz{
    \npublic String id {get;private set;}
    \npublic Xyz(){
    \nid = Account.sObjectType.getDescribe().getRecordTypeInfosByName().get(\u2018test\u2019).getRecordTypeId();
    \n}
    \n}<\/code>
    \nThis will cause a repeated execution of the sObject getDescribe() method, resulting in a breach of the total number of described governor limits if the code operates against more than 100 records. \t\t\t\t\t\t\t<\/p>\n

    Solution<\/strong>
    \nTo resolve this problem we need to implement the Singleton pattern in Apex, the class must instantiate only a single instance and be globally accessible. It is implemented by: <\/p>\n