In some situations the type handled by a constructor is only known at
runtime, in which case the constructor needs to know what class must be
used to instantiate the object.
For instance, an interface may declare a static constructor that is then
implemented by several child classes. One solution would be to register
the constructor for each child class, which leads to a lot of
boilerplate code and would require a new registration each time a new
child is created. Another way is to use the attribute
`\CuyZ\Valinor\Mapper\Object\DynamicConstructor`.
When a constructor uses this attribute, its first parameter must be a
string and will be filled with the name of the actual class that the
mapper needs to build when the constructor is called. Other arguments
may be added and will be mapped normally, depending on the source given
to the mapper.
```php
interface InterfaceWithStaticConstructor
{
public static function from(string $value): self;
}
final class ClassWithInheritedStaticConstructor implements InterfaceWithStaticConstructor
{
private function __construct(private SomeValueObject $value) {}
public static function from(string $value): self
{
return new self(new SomeValueObject($value));
}
}
(new \CuyZ\Valinor\MapperBuilder())
->registerConstructor(
#[\CuyZ\Valinor\Attribute\DynamicConstructor]
function (string $className, string $value): InterfaceWithStaticConstructor {
return $className::from($value);
}
)
->mapper()
->map(ClassWithInheritedStaticConstructor::class, 'foo');
```
The mapper is now more type-sensitive and will fail in the following
situations:
- When a value does not match exactly the awaited scalar type, for
instance a string `"42"` given to a node that awaits an integer.
- When unnecessary array keys are present, for instance mapping an array
`['foo' => …, 'bar' => …, 'baz' => …]` to an object that needs only
`foo` and `bar`.
- When permissive types like `mixed` or `object` are encountered.
These limitations can be bypassed by enabling the flexible mode:
```php
(new \CuyZ\Valinor\MapperBuilder())
->flexible()
->mapper();
->map('array{foo: int, bar: bool}', [
'foo' => '42', // Will be cast from `string` to `int`
'bar' => 'true', // Will be cast from `string` to `bool`
'baz' => '…', // Will be ignored
]);
```
When using this library for a provider application — for instance an API
endpoint that can be called with a JSON payload — it is recommended to
use the strict mode. This ensures that the consumers of the API provide
the exact awaited data structure, and prevents unknown values to be
passed.
When using this library as a consumer of an external source, it can make
sense to enable the flexible mode. This allows for instance to convert
string numeric values to integers or to ignore data that is present in
the source but not needed in the application.
---
All these changes led to a new check that runs on all registered object
constructors. If a collision is found between several constructors that
have the same signature (the same parameter names), an exception will be
thrown.
```php
final class SomeClass
{
public static function constructorA(string $foo, string $bar): self
{
// …
}
public static function constructorB(string $foo, string $bar): self
{
// …
}
}
(new \CuyZ\Valinor\MapperBuilder())
->registerConstructor(
SomeClass::constructorA(...),
SomeClass::constructorB(...),
)
->mapper();
->map(SomeClass::class, [
'foo' => 'foo',
'bar' => 'bar',
]);
// Exception: A collision was detected […]
```
