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#DD Map<ID, List<Contacts>> what is the rationale of using list in maps?
I was gong through the Apex code and found out a code line;
Map<ID, List<Contacts>> mapCntList1 = new Map<ID, List<Contacts>>();
I was wondering this statement could have been written like this also;
Map<ID, Contacts> mapCntList2 = new Map<ID, Contacts>();
If the list declaration in "mapCntList1" is correct, can anyone tell when this should be used and when "mapCntList2" should be used?
Thanks
Map<ID, List<Contacts>> mapCntList1 = new Map<ID, List<Contacts>>();
I was wondering this statement could have been written like this also;
Map<ID, Contacts> mapCntList2 = new Map<ID, Contacts>();
If the list declaration in "mapCntList1" is correct, can anyone tell when this should be used and when "mapCntList2" should be used?
Thanks
In case of mapCntList1, List<Contacts> (I suppose, this is List<Contact> not List<Contacts>), must be a valid data type, and this would create a map that has a list of contacts for each given id.
For second case, if you wanna use "Map<ID, Contacts>" ( Again, I suppose, this is Contact not Contacts) , you can use it that way, but notice, this will create a map that has a contact (not list) for each given id.
You may refer below link for more details.
https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/langCon_apex_collections_maps.htm
Please check the link below
https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/langCon_apex_collections_maps.htm
Best Regards
Naga kiran
1) As Suraj said it is Contact not Contacts and if it is Contacts it should be like Contacts__c because every custom objects must end with __c.
2) a) mapCntList1 - Refers to a map in which every key(ID) is associated with lists if contact . 1 key --> list of contact(contact Records say-c1,c2,c3,c4)
b) mapCntList2 - Refers to a map in which every key(ID) is associated with a single instance of contact or you can say a single contact record .
1key --> Single instance if contact (contact Record say - Con1)
Now both of them are different
1) If you come across a scenario where your key will be associated with list of contacts use mapCntList1 . for e.g. 1 ID(Say Account ID) have multiple Contact
2) In rather case use mapCntList2.
List<Account> lstAccount = [SELECT Id, (SELECT Id, Name FROM Contacts) FROM Account where id='00100000000ABCD'];
for(Account lstAcc : lstAccount)
{
mapAccCon.put(lstAcc.id, lstAcc.Contacts);
}
System.debug(mapAccCon);