Add toLabel function (#43)

This fixes issue #41

src/classes/Query.cls

@@ -146,6 +146,16 @@ public class Query {
         return this;
     }
 
+    public Query toLabel(String field) {
+        functionFieldList.add(new FunctionFieldTuple(TO_LABEL, field));
+        return this;
+    }
+
+    public Query toLabel(String field, String alias) {
+        functionFieldList.add(new FunctionFieldTuple(TO_LABEL, field, alias));
+        return this;
+    }
+
     public Query max(String field) {
         functionFieldList.add(new FunctionFieldTuple(MAX, field));
         return this;
@@ -1545,6 +1555,7 @@ public class Query {
     private final String SUM = 'SUM';
     private final String COUNT = 'COUNT';
     private final String COUNT_DISTINCT = 'COUNT_DISTINCT';
+    private final String TO_LABEL = 'TOLABEL';
 
     // Object Schema variables
     private String objectName;

src/classes/QueryTest.cls

@@ -957,6 +957,31 @@ public class QueryTest {
         System.assertEquals(result.get('expr5'), 16);
     }
 
+    @isTest
+    static void toLabelTest() {
+        Account acc1 = new Account(Name = 'New Account 1');
+
+        insert acc1;
+
+        Opportunity opp = new Opportunity(
+                AccountId = acc1.Id,
+                Name = 'New Opportunity',
+                CloseDate = Date.today().addDays(3),
+                TotalOpportunityQuantity = 10,
+                StageName = 'New');
+        insert opp;
+
+        List<Opportunity> opp0 = new Query('Opportunity').
+                selectField('Id').
+                toLabel('StageName').addConditionEq('Id', opp.Id).run();
+        System.assertEquals(opp0[0].get('StageName'), 'New');
+
+        List<Opportunity> opp1 = new Query('Opportunity').
+                selectField('Id').
+                toLabel('StageName', 'myStageName').addConditionEq('Id', opp.Id).run();
+        System.assertEquals(opp1[0].get('myStageName'), 'New');
+    }
+
     @isTest
     static void groupByTest() {
         Account acc1 = new Account(Name = 'Account 1', Rating = '1', NumberOfEmployees = 1);