Apex Developer Guide
jsObject Map Considerations
Be cautious when using sObjects as map keys. Key matching for sObjects is based on the comparison
of all sObject field values. If one or more field values change after adding an sObject to the
map, attempting to retrieve this sObject from the map returns null. This is because the modified sObject isn’t found in the map due to different
field values. This can occur if you explicitly change a field on the sObject, or if the sObject
fields are implicitly changed by the system; for example, after inserting an sObject, the sObject
variable has the ID field autofilled. Attempting to fetch this Object from a map to which it was
added before the insert operation won’t yield the map
entry, as shown in this example.
1// Create an account and add it to the map
2Account a1 = new Account(Name='A1');
3Map<sObject, Integer> m = new Map<sObject, Integer>{
4a1 => 1};
5
6// Get a1's value from the map.
7// Returns the value of 1.
8Assert.areEqual(1, m.get(a1));
9// Id field is null.
10Assert.isNull(a1.Id);
11
12// Insert a1.
13// This causes the ID field on a1 to be auto-filled
14insert a1;
15// Id field is now populated.
16Assert.isNotNull(a1.Id);
17
18// Get a1's value from the map again.
19// Returns null because Map.get(sObject) doesn't find
20// the entry based on the sObject with an auto-filled ID.
21// This is because when a1 was originally added to the map
22// before the insert operation, the ID of a1 was null.
23Assert.isNull(m.get(a1));