Converting a list of objects to a list of string without iteration

Question

I need a comma separated list of Names of a custom object. I tried the below code.

List<string> lstNames = new List<string>();
lstNames = [Select Name from A__c where field__c =: objB.Id ];
string Names = string.join(lstNames,',')

It gives me an error that Illegal assignment from List to List. I know it is because I am trying to convert a list of A__c to a list of string. Is there a way available to convert a list of object to a list of string without iterating through each record or to get a comma separated list of values without iteration?

Answer 1

This should work:

List<String> lstNames = new List<String>();
for(A__c ac: [Select Name from A__c where field__c =: objB.Id]){
    lstNames.add(ac.Name);
}
String names = string.join(lstNames,',');
System.debug(names);

Your code not works because you are trying to assign an object to a string.

-edit In my opinion, this is not possible without loop.

Answer 2

Do something like this:

string s = [select name from A__c where field__c =: objB.Id ].name; //if it returns only 1 record. 
system.debug('s=='+s);
list<string> lstNames = new list<string>();
lstNames.add(s);
string Names = string.join(lstNames,',');
system.debug('Names='+Names);

Answer 3

Please use below code snippet, it should work fine. Let's assume the object is Account.

List<AggregateResult> accList= [select name from Account group by name]; 
String str = JSON.serialize(accList);
str = str.removeStart('[{"attributes":{"type":"AggregateResult"},"Name":"');
str= str.replace('"},{"attributes":{"type":"AggregateResult"},"Name":"',',');
Str= str.removeEnd('"}]');

system.debug('Names='+str);