Select all fields in a custom object dynamically in a specific order

Question

I have a custom object that I need to select all fields from in a specific order to create a text file in a specific format. So far, I've been dynamically accessing all the fields I need via .getMap().

Map<String, Schema.SObjectField> objectFields = Schema.getGlobalDescribe().get('Custom_Object__c').getDescribe().fields.getMap();
        fieldLabels = objectFields.values();
        for(String fieldName : objectFields.keyset())
        {
            if(commaSeparatedFields == null || commaSeparatedFields == ''){
                commaSeparatedFields = fieldName;
            }else{
                commaSeparatedFields = commaSeparatedFields + ', ' + fieldName;
            }
        }
Database.getQueryLocator('select ' + commaSeparatedFields + ' from Custom_Object__c');

The problem is that the fields aren't in the order I want. I could of course hard-code the field names into the query, but the second one field changes, etc. my code will break.

Any suggestions of how to specify field order some other way? I was thinking if I could add custom metadata to each field and give them a priority to order by, then I could maybe access that metadata when compiling them into 'commaSeparatedFields' and then be able to order them dynamically. Not sure how to do this though. Any suggestions are appreciated.

Answer 1

In the past I have used FieldSet for similar requirements but now that I check again the order is ensured in Visualforce but not explicitly ensured in Apex.

Alternatively, one can implement this with a new Custom Metadata Type. The order can be set via a field and you query in your code to retrieve them in the defined order. Additionally Custom Metadata records can be maintained in your code repository and they can be deployed together with your code.

There's a cool Trailhead explaining more details on how to use them