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Clayton HilteClayton Hilte 

Get from Map using a value in a List

Hi all,

I have a Trigger on the Task object. I am trying to perform a get from a Map using an ID from a previoulsy populated List. The list will only every have 1 ID in it, but I still need to tell it which ID to use. Now I could simply use the WhoId, but without going into detail I can't use that for other reasons based on how the trigger will function. 

Based on the code below, is this correct?
-------------------------------------------------------------------------

trigger ContactAccountLastActivity on Task (after insert, after update) {

    List<String> lstWhoIds = new List<String>();

for( Task t : Trigger.new )
    {
        // Add the "Who" from the task to the lstWhoIds List
        lstWhoIds.add(t.WhoId);    
    }
    
        // Query Contact Object to get Contact fields and create
        // a Map of Contact ID to Contact fields using lstContactFields Query results
    List<Contact> lstContactFields = new List<Contact>([SELECT Id, AccountId, Last_Contacted_Date__c, Last_Contacted_By__c
                                                     FROM Contact
                                                     WHERE Id in :lstWhoIds]);
    Map<String, Contact> mapWhoIds = new Map<String, Contact>(lstContactFields);

for( task t : Trigger.new )
    {
            if( (t.type == 'Telephone In' || t.type == 'Telephone Out' || t.type == 'Visit/Meeting') && t.status == 'Completed' )
            {
                if( Date.valueOf(t.Completed_Date__c) >= mapWhoIds.get(lstWhoIds).Last_Contacted_Date__c )
                {
                    mapWhoIds.get(lstWhoIds[0]).Last_Contacted_Date__c = Date.valueOf(t.Completed_Date__c);
                }
        }
}

mapWhoIds.get(lstWhoIds[0]).Last_Contacted_Date__c  does not provide any errors
mapWhoIds.get(lstWhoIds).Last_Contacted_Date__c  give error: "Incompatible key type LIST<String> for MAP<String, Contact>
 
Best Answer chosen by Clayton Hilte
Balaji BondarBalaji Bondar
Hi Clay,
Below code will help.used string to find the value as below: 
for( task t : Trigger.new )
    {
            if( (t.type == 'Telephone In' || t.type == 'Telephone Out' || t.type == 'Visit/Meeting') && t.status == 'Completed' )
            {
                if( Date.valueOf(t.Completed_Date__c) >= mapWhoIds.get(lstWhoIds).Last_Contacted_Date__c )
                {
                    String lstWhoIdsString = lstWhoIds[0];
					mapWhoIds.get(lstWhoIdsString).Last_Contacted_Date__c = Date.valueOf(t.Completed_Date__c);
                }
        }
}
Important :
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All Answers

Balaji BondarBalaji Bondar
Hi Clay,
Below code will help.used string to find the value as below: 
for( task t : Trigger.new )
    {
            if( (t.type == 'Telephone In' || t.type == 'Telephone Out' || t.type == 'Visit/Meeting') && t.status == 'Completed' )
            {
                if( Date.valueOf(t.Completed_Date__c) >= mapWhoIds.get(lstWhoIds).Last_Contacted_Date__c )
                {
                    String lstWhoIdsString = lstWhoIds[0];
					mapWhoIds.get(lstWhoIdsString).Last_Contacted_Date__c = Date.valueOf(t.Completed_Date__c);
                }
        }
}
Important :
If this is what you were looking for then please mark it as a "SOLUTION" or You can Click on the "Like" Button if this was beneficial for you.
This was selected as the best answer
Anoop AsokAnoop Asok
The parameter to a Map's get method should be the same type as that of the Key. In your case, the Key is of type string, but the parameter being passed is a List<String>. Changing the RHS to mapWhoIds.get(lstWhoIds[0]).Last_Contacted_Date__c might take out that error message, but to solve your problem I guess you should be using t.whoId instead of listWhoIds[0].

Thanks,
Anoop
Clayton HilteClayton Hilte
@Anoop - I don't get the error when I specify the position in the list such as (lstWhoIds[0]). It seems to me that the error is occurring because it is attempting to put the entire list as a single Unique Key. Testing it with the position [0] worked fine on my debug logs.

@Balaji - I like the idea of initiatlizing another var String before passing the update values. I don't think there will be any difference, but it is cleaner code and might be better practice. Thanks!