getTechiewithSmriti: Map methods in Salesforce

Map methods in Salesforce

Maps are a critical data type to get to know when developing on the Force.com platform

A map is a collection of key-value pairs where key should be unique and value can be duplicated.
Keys and values can be any data type—primitive types, collections, sObjects, user-defined types, and built-in Apex types.
Map keys of type String are case-sensitive
Map keys can contain up to only four levels of nested collections.
A map key can hold the null value.
Adding a map entry with a key that matches an existing key in the map overwrites the existing entry with that key with the new entry.
Uniqueness of map keys of user-defined types is determined by the equals and hashCode,which we provide in your classes.
Uniqueness of keys of all other non-primitive types, such as sObject keys, is determined by comparing the objects’ field values.

Syntax:

  Map<Key,Value> variablename=new Map<Key,Value>();

Instantiating a Map

Map<integer, string> mapName = new Map<integer, string>();

If you have a list of sObjects you can just pass that list in the constructor

Map<Id, Account> accountsById = new Map<Id, Account>(listOfAccounts);

Method available with map are:

keySet()
values()
get(Keyid)
put(key,value)
putAll(fromMap)
putAll(sobjectArray)
containskey(key)
clear()
size()
clone()
isEmpty()
remove(key)
deepClone()
equals(map2)
getSobjectType()
hashCode()

Example:

Let's make a map that gives us tourist attraction places when we search for country.

put(key, value)

/ Step 1: The search term (tourist attraction) data type will be a string
// The search result (location) data type will also be a string
Map<String, String> tourismMap = new Map<String, String>();

// Step 2: Add search term/result pair
tourismMap.put('Egypt','Great Pyramid of Giza');
tourismMap.put('Paris', 'Eiffel Tower');
tourismMap.put('Los Angeles', 'Hollywood Sign');
tourismMap.put('Japan', 'Mount Fuji');
tourismMap.put('London', 'Tower of London');
tourismMap.put('Germany', 'Neuschwanstein Castle');
tourismMap.put('Japan', 'Mount Fuji');
tourismMap.put('India', 'Taj Mahal');

get(key)
This method returns the value of the specified key which is mapped, or it returns null if the map contains no value for this key

// Step 1: The search term (tourist attraction) data type will be a string
// The search result (location) data type will also be a string
Map<String, String> tourismMap = new Map<String, String>();
// Step 2: Add search term/result pair
tourismMap.put('London', 'Tower of London');
tourismMap.put('Germany', 'Neuschwanstein Castle');
tourismMap.put('India', 'Taj Mahal');
// Step 3: Search our map using the get() function
String name = tourismMap.get('Germany');
system.assertEquals('Neuschwanstein Castle', name)

putAll(fromMap)
Copies all of the mappings from the specified map to the original map.

Map<String, String> tourismMap1 = new Map<String, String>();
tourismMap1.put('Egypt','Great Pyramid of Giza');
tourismMap1.put('Paris', 'Eiffel Tower');
tourismMap1.put('Los Angeles', 'Hollywood Sign');
tourismMap1.put('Japan', 'Mount Fuji');

Map<String, String> tourismMap2 = new Map<String, String>();
tourismMap2.put('London', 'Tower of London');
tourismMap2.put('Germany', 'Neuschwanstein Castle');
tourismMap2.put('Japan', 'Mount Fuji');
tourismMap2.put('India', 'Taj Mahal');

// Add map1 entries to map2
tourismMap2.putAll(tourismMap1);
system.debug(tourismMap2.values());

remove(key)
This method removes the mapping for the specified key from the map, if present, and returns the corresponding value.

Map<String, String> tourismMap = new Map<String, String>();
tourismMap.put('Egypt','Great Pyramid of Giza');
tourismMap.put('Paris', 'Eiffel Tower');
tourismMap.put('Los Angeles', 'Hollywood Sign');

//removes the mapping for the specified key from the map
tourismMap.remove('Paris');
system.debug(tourismMap);

values()
This methods returns a list which contains all the values in the map.The values are returned in an arbitrary order.

Map<String, String> tourismMap = new Map<String, String>();
tourismMap.put('Egypt','Great Pyramid of Giza');
tourismMap.put('Paris', 'Eiffel Tower');
tourismMap.put('Los Angeles', 'Hollywood Sign');

//create list to return all the values in the map
List<String> mapValues = new List<String>();
mapValues = tourismMap.values();
system.debug(mapValues);

getSObjectType()
This method returns the value of the sObject type in format of key and value.

Map <id,Account>acctMap = new map<id,account>([select  name from  Account limit 5]);
for(string accValue:acctmap.keyset()){
system.debug(acctmap.get(accValue));
}

keyset()
Returns a set that contains all of the keys in the map.

Map<String, String> tourismMap = new Map<String, String>();
tourismMap.put('Egypt','Great Pyramid of Giza');
tourismMap.put('Paris', 'Eiffel Tower');
tourismMap.put('Los Angeles', 'Hollywood Sign');
//set to hold keys of map
Set <String> mapKeys = new Set<String>();
mapKeys = tourismMap.keySet();
// return the list of the keys 
system.debug(mapKeys);

size()

Return the number of components in the map.

Map<String, String> tourismMap = new Map<String, String>();
tourismMap.put('Egypt','Great Pyramid of Giza');
tourismMap.put('Paris', 'Eiffel Tower');
tourismMap.put('Los Angeles', 'Hollywood Sign');
Integer mapSize = tourismMap.size();
// return the size of the map 
system.debug(mapSize);

clear()

Removes all of the key-value mappings from the map.

Map<String, String> tourismMap = new Map<String, String>();
tourismMap.put('Egypt','Great Pyramid of Giza');
tourismMap.put('Paris', 'Eiffel Tower');
tourismMap.put('Los Angeles', 'Hollywood Sign');
tourismMap.clear();

clone()

Makes duplicate copy of the map

Map<String, String> tourismMap = new Map<String, String>();
tourismMap.put('Egypt','Great Pyramid of Giza');
tourismMap.put('Paris', 'Eiffel Tower');
tourismMap.put('Los Angeles', 'Hollywood Sign');

//Makes duplicate copy of the map
Map<String, String> cloneMap = new Map<String, String>();
cloneMap = tourismMap.clone();
system.debug(cloneMap);

containsKey(key)

Returns true if the map contains a mapping for the specified key.

Map<String, String> tourismMap = new Map<String, String>();
tourismMap.put('Egypt','Great Pyramid of Giza');
tourismMap.put('Paris', 'Eiffel Tower');
tourismMap.put('Los Angeles', 'Hollywood Sign');

Boolean contains = tourismMap.containsKey('Paris');
//Returns true if the map contains a mapping for the specified key.
System.assertEquals(true, contains);

hashCode()

Returns the hashcode corresponding to this map.

Map<String, String> tourismMap = new Map<String, String>();
tourismMap.put('Egypt','Great Pyramid of Giza');
tourismMap.put('Paris', 'Eiffel Tower');
tourismMap.put('Los Angeles', 'Hollywood Sign');

//Returns the hashcode corresponding to this map.
Integer storeHashCode = tourismMap.hashCode();
system.debug(storeHashCode);

isEmpty()

Returns true if the map has zero key-value pairs.

Map<String, String> tourismMap = new Map<String, String>();
tourismMap.put('Egypt','Great Pyramid of Giza');
tourismMap.put('Paris', 'Eiffel Tower');
tourismMap.put('Los Angeles', 'Hollywood Sign');

Boolean empty = tourismMap.isEmpty();
//Return true if map has zero key-value pair
System.assertEquals(true, empty);

Scenarios:

1) When moving line items from one opportunity to other opportunity we need to use map
2) to determine whether an old value is changed or not in a trigger we need to use map

References:

https://www.sfdc-lightning.com/2018/09/collection-in-salesforce.html
https://blog.jeffdouglas.com/2011/01/06/fun-with-salesforce-collections/

https://www.sundoginteractive.com/blog/apex-why-maps-are-your-friend
https://www.janbasktraining.com/blog/map-in-salesforce/
https://www.iterativelogic.com/working-with-apex-code-maps/