Mapping in apex [closed]

Question

Best way to loop through two objects

Answer 1

There are two parts to your question. First making a dynamic query based on the results that you have fetched from custom metadata.

Assuming your provided metadata example.

Id      Field 
id-123  field1__c
id-456  field2__c

The dynamic query can be created in the following manner.

//query the metadata
List<CaseField_mdt> metalist = [SELECT Id, Field FROM CaseField_mdt];

/*Now since you want the final results in key-value format where your key is 
  metadata field, so you create a map, to keep key-value mapping. This will 
  help in creating the query as well as generating the results in required 
  format.
*/

Map<String, String> fmap = new Map<String, String>();
for(CaseField_mdt m : metalist) {
  fmap.put(m.Field, m.Id);
}

Now In order to create your dynamic query on Case, you can use the map keys, to form a string, and query those required fields.

String query_str = 'SELECT' + String.join(new List<String>(fmap.keySet()), ', ') + ' FROM Case';

//execute your dynamic query
List<Case> cases = database.query(query_str);

//Create Your final result Map in required format
Map<String, sObject> result = new Map<String, sObject>();
for(Case c : cases) {
 for(String key : fmap.KeySet()) {
  if(c.get(key) != null) // field exists in case
    result.put(fmap.get(key) , c.get(key)); // {id-123: case1 }
  }
}

System.debug('Result : ' + result); // This map will print your required format results.