Mapping Table

When we tell the mapper to map a source to a target, it will look up the mapping table to find the correct transformer for the job, then tells the transformer to do the mapping. It does that first for the root source and target pair, then traverses down the properties and does the same for each property.

Each transformer supplies a list of supported source to target mappings. The mapping table is constructed from the source and target types supported by each of the transformers registered in the system.

Mapping Table Properties

A row in the mapping table has the following properties:

• Ordering number. Transformers have a priority. A mapping entry generated by a transformer with a higher priority will be checked earlier than those generated by one with a lower priority.
• Source and target type pair.
• Target variance. Invariant means the target type must be exactly the same as specified in the mapping table. Variant means the target type can also be a subclass of the type specified in the mapping table. Note that the source type is always variant.
• Transformer service ID.

Viewing the Mapping Table

To inspect the mapping table, you can use the rekalogika:mapper:mapping command:

$ php bin/console rekalogika:mapper:mapping

The Mapper panel of the Symfony Profiler also shows the mapping table.

Default Mapping Table

Ordering	Source Type	Target Type	Target Variance	Class
1	null	null	invariant	NullToNullTransformer
2	int	int	invariant	ScalarToScalarTransformer
3	int	float	invariant	ScalarToScalarTransformer
4	int	string	invariant	ScalarToScalarTransformer
5	int	bool	invariant	ScalarToScalarTransformer
6	float	int	invariant	ScalarToScalarTransformer
7	float	float	invariant	ScalarToScalarTransformer
8	float	string	invariant	ScalarToScalarTransformer
9	float	bool	invariant	ScalarToScalarTransformer
10	string	int	invariant	ScalarToScalarTransformer
11	string	float	invariant	ScalarToScalarTransformer
12	string	string	invariant	ScalarToScalarTransformer
13	string	bool	invariant	ScalarToScalarTransformer
14	bool	int	invariant	ScalarToScalarTransformer
15	bool	float	invariant	ScalarToScalarTransformer
16	bool	string	invariant	ScalarToScalarTransformer
17	bool	bool	invariant	ScalarToScalarTransformer
18	string	DateTimeInterface	invariant	DateTimeTransformer
19	string	DateTime	invariant	DateTimeTransformer
20	string	DateTimeImmutable	invariant	DateTimeTransformer
21	string	DatePoint	invariant	DateTimeTransformer
22	DateTimeInterface	DateTimeInterface	invariant	DateTimeTransformer
23	DateTimeInterface	DateTime	invariant	DateTimeTransformer
24	DateTimeInterface	DateTimeImmutable	invariant	DateTimeTransformer
25	DateTimeInterface	DatePoint	invariant	DateTimeTransformer
26	DateTimeInterface	string	invariant	DateTimeTransformer
27	string	BackedEnum	variant	StringToBackedEnumTransformer
28	MapToObjectInterface	object	variant	ClassMethodTransformer
29	object	MapFromObjectInterface	variant	ClassMethodTransformer
30	Stringable	string	invariant	ObjectToStringTransformer
31	UnitEnum	string	invariant	ObjectToStringTransformer
32	Traversable	Collection	invariant	TraversableToArrayAccessTransformer
33	Traversable	ReadableCollection	invariant	TraversableToArrayAccessTransformer
34	Traversable	ArrayCollection	invariant	TraversableToArrayAccessTransformer
35	Traversable	ArrayObject	invariant	TraversableToArrayAccessTransformer
36	Traversable	ArrayIterator	invariant	TraversableToArrayAccessTransformer
37	Traversable	ArrayAccess	invariant	TraversableToArrayAccessTransformer
38	Traversable	CollectionInterface	invariant	TraversableToArrayAccessTransformer
39	Traversable	array	invariant	TraversableToArrayAccessTransformer
40	array	Collection	invariant	TraversableToArrayAccessTransformer
41	array	ReadableCollection	invariant	TraversableToArrayAccessTransformer
42	array	ArrayCollection	invariant	TraversableToArrayAccessTransformer
43	array	ArrayObject	invariant	TraversableToArrayAccessTransformer
44	array	ArrayIterator	invariant	TraversableToArrayAccessTransformer
45	array	ArrayAccess	invariant	TraversableToArrayAccessTransformer
46	array	CollectionInterface	invariant	TraversableToArrayAccessTransformer
47	array	array	invariant	TraversableToArrayAccessTransformer
48	Traversable	Traversable	invariant	TraversableToTraversableTransformer
49	array	Traversable	invariant	TraversableToTraversableTransformer
50	object	array	invariant	ObjectToArrayTransformer
51	array	object	variant	ArrayToObjectTransformer
52	object	object	variant	ObjectToObjectTransformer
53	null	string	invariant	NullTransformer
54	null	int	invariant	NullTransformer
55	null	float	invariant	NullTransformer
56	null	bool	invariant	NullTransformer
57	null	array	invariant	NullTransformer
58	mixed	null	invariant	NullTransformer
59	mixed	mixed	variant	CopyTransformer