Some background of what I did so far, I took a set of Ids out of User that are 'PowerPartners', and with those Id's I search for them in Group Members. Now I have a groupList, and with that groupList I want to check and see if when a Lead is created if it is in that list. I'll post my code below, and the things I tried.. (Some are obviously wrong)

if(groupList.containsKey(ld.CreatedById)) --Method Does not exist or incorrect signature 
if(groupList.get(ld.CreatedById)) --Method Does not exist or incorrect 
if(groupList.contains(ld.CreatedById))--Method Does not exist or incorrect 
if(groupList == ld.CreatedById) --Comparison arguments must be compatible types

Trigger

List<GroupMember>groupList = new List<GroupMember>([select GroupId,UserOrGroupId from GroupMember where UserORGroupID IN:pUserMap]);
System.debug('groupList '+groupList );
if(pUserMap != null){
//System.debug('Inside PartUserMap != null');
for(Lead ld: trigger.new){    
        if(groupList.containsKey(ld.CreatedById)){ //Need help here      
        LeadShare ldShare = new LeadShare (LeadId = ld.id, LeadAccessLevel =  'Edit');   
        leadShareList.add(ldShare );
        }       
} 
}

Attribution to: EricSSH

Possible Suggestion/Solution #1

This is because your groupList is a list and the containsKey() method is for Maps not Lists

You have to change your first line of code 'query' to something like this :

Map<Id, GroupMember> groupMap = new Map <Id, GroupMember>();
for(GroupMember grp : [select GroupId, UserOrGroupId from GroupMember where UserORGroupID IN:pUserMap])
    groupMap.put(grp.UserOrGroupId, grp);

Then this line of code should work just fine

 if(groupMap.containsKey(ld.CreatedById))

Attribution to: melmoussaoui
This content is remixed from stackoverflow or stackexchange. Please visit https://salesforce.stackexchange.com/questions/33731