A Look inside
The Illuminate Container

Ian Littman / @iansltx

Laravel Austin, March 2019

https://ian.im/LC0319

Not gonna talk about facades

They're an antipattern

...and I need to clean up some code I have that uses them...

...and on-the-fly facades are some level 70 autoloader voodoo.

Docs!

Binding classes

• bind() (or singleton() for shared classes)
  • null second param copies first param (for setting a class to be bound as a singleton)
  • bindIf() - bind if not bound
  • offsetSet($k, $v), __set() - bind(), wrap $v in a closure returning $v if it isn't a closure already
• Contextual Binding
  • when()->needs()->give()
  • addContextualBinding($concrete, $abstract, $impl)
• instance() - Provide an already-instantiated class as the destination of a dependency
  • forgetInstance($abstract) + forgetInstances() exist

Binding classes, Part 2

• Binding checks
  • bound/has/offsetExists() - bindings, instances, aliases
  • resolved() - resolved, instances, aliases
  • getBindings()
• Tags
  • tag() - assign an identifier to one or more tags
  • tagged() - iterable of resolved deps assigned to a tag
• Aliases
  • alias() - Map a concrete class name to an interface
  • getAlias() - Returns the mapping set by alias()

Binding classes, Part 3

• extend() - Wrap a dep in a closure($dep, $container)
  • forgetExtenders($abstract) exists
• Rebinding
  • rebinding($abstract, $cb) - call $cb($instance, $container) any time $abstract is rebound
  • refresh($abstract, $target, $method) - call $method on $target with $instance as a param on-rebind
• offsetUnset($k) drops from bindings/instances/resolved
• flush() drops all bindings/aliases/resolved classes

Resolving Classes

• make($abstract, $params) allows param overrides
• makeWith() is the same as make()
• offsetGet(), __get() are the same as single-arg make()
• factory($abstract) returns a Closure that calls make()
• get($abstract) is a PSR-11 compliant (exceptions) make()
• Events - can be global or specific to an abstract
  • Global callbacks in a group are fired first
  • $callback($instance, $container)
  • Return value is unused
  • resolving()
  • afterResolving() - fired immediately after resolving()

get ready for some Reflection

Resolve() and Build()

Method bindings

• bindMethod($method, $callback)
  • $method can be Class@method or array-style
• hasMethodBinding()
• callMethodBinding($method, $instance)
  • $instance is first param passed to the bound method
  • Container is second

injecting callables with call() and BoundMethod::call()

You can also curry closures with wrap($closure, $params = [])

Static Methods

• getInstance()
• setInstance()

Compare(5.5, 5.7)

• [5.6] More flexibility in method injection params
• [5.6] bindMethod() can use [MyClass::class, 'method'] syntax for first param, in addition to 'MyClass@method'
• [5.7] Contextual binding can be configured on multiple target classes at once
• [5.7] get() (PSR-11) returns autowired dependencies

Compare(5.7, 5.8)

• getClosure() returned function uses resolve() with on-resolve callbacks turned off (an ability itself added in 5.8) instead of make()
• tagged() iteratively builds bindings instead of building an array all at once (using a RewindableGenerator, which is now included in the package)
• Trying to alias a thing to itself is now caught on alias() rather than waiting until getAlias()
• Various docblock fixes

Bonus: Service Providers
(more info for package devs)

Thanks! QUestions?

Slides: ian.im/LC0319 (and I'm @iansltx)