Get Id of object in trigger?

Question

My problem is this. When a user changes the status on a Case object, I want to see if they changed that status to closed. If so, I want to do some checks to see if I am going to allow that.

What I have so far is this

trigger CaseClosed on Case (before update) {

    // Check if the trigger's status is being changed to closed.
    List<Case> newCases = Trigger.new;
    Case newCase;

    for( Case c : newCases ) {
        if( Case.CaseNumber === c.CaseNumber ) {
            newCase = c;
        }
    }

My issue is that I don't know how to get the Id, CaseNumber, or whatever the unique identifier of a case is. In a trigger I've written previously I was able to use a UserInfo object and do UserInfo.getUserId() in the if statement. However, I don't see anything like that available for Case objects.

Answer 1

The ID of any record is always just Id.

For example, to see if the case was closed this transaction:

trigger doSomethingOnCases on Case (before update) {
    Case[] closingCases = new Case[0];
    for(Case record:Trigger.new)
        if(record.IsClosed && !Trigger.oldMap.get(record.Id).IsClosed)
            closingCases.add(record);
    // For each record, see if we'll allow the close.
    // closingCases now contains all cases that will be closed when transaction completes.
}

Every record in salesforce.com has an ID value. You can always depend on this field being present. It isn't documented under any specific object because it applies globally across all objects.

Answer 2

The answer asked for how to do this in a trigger, and sfdcfox gave a great answer.

It might be easier to use to create a Workflow Rule instead of a trigger. But this wholly depends on what you want to do once you identified Cases that changed their status to Closed. If it's simple like set the datetime field Closed_Datetime__c to the current time, workflows are great. If it's complex, stick to the trigger (though with the added maintenance cost of test code...).

How to write Workflow Rules: https://login.salesforce.com/help/doc/en/creating_workflow_rules.htm