Iterate over all fields of all FieldSet of an SObject

Question

Just posting this because it took me a bit of time to get my answer. For anyone wanting to get a list of all the Fields present on all the FieldSets of an Object, here is my method.

Hope it will be usefull for someone day.

Answer 1

private String getUsedFields() {
    Set<String> usedFields = new Set<String>();
    for (String fieldSet : Schema.SObjectType.'SObject'.fieldSets.getMap().keySet()) {
        for (Schema.FieldSetMember field : Schema.SObjectType.'SObject'.fieldSets.getMap().get(fieldSet).getFields()) {
            usedFields.add(field.getFieldPath());
        }
    }
    
    List<String> fieldList = new List<String>(usedFields);
    String fields = String.join(fieldList, ', ');
    return fields;
}

Replace 'SObject in my code by the APi name of your SObject.

If you want to have duplicate, use a List instead of a set.

the String.Join() at the end is useful if you want to transform your list into a string with your values sepparated by commas to use in a Database.query like me. and you must transform your Set into a List if you want to do it.