ludovicdeluna / sector

Simple Injector; Dependency Injection

sector

sector - for Simple Injector - provides a Dependency Injection mechanism for Go.

Put it simply, sector fills pointers with values come from factories. So we have the factory - the constructor (role) - and the injector.

A factory implements the Factory interface. In it's simplest form, it's just a function with this signature, func(interface{}) bool and uses the Go's type switch to fill the pointers:

func myFactory(ptr interface{}) bool {
	switch x := ptr.(type) {
	case *int:
		*x = 1001
	case *string:
		*x = `injected string`
	case *Trait:
		buffer := Trait{}
		*x = buffer
	case *Data:
		buffer := Data{}
		*x = buffer
	case *map[string]interface{}:
		*x = make(map[string]interface{})
		(*x)[`asset`] = `another injected string`
	case *SI:
		v := SIO{`yet another injected string`}
		*x = &v
	case *[]int:
		*x = []int{1, 2, 3}
	default:
                // this factory does not fill pointers of this type
		return false
	}

	return true
}

Then we use this factory in our injector to fill in the fields of a struct.

dj := NewInjector(FactoryFunc(genericFactory))

Now we use this injector to inject desired values into struct's fields.

var s Sample
dj.Inject(&s)

Fields that are tagged with inject:"+" will get filled with proper value from the factory. Fields tagged with inject:"*" will get filled recursively down the tree.

type Sample struct {
	Trait `inject:"*"`      // inject field, recursively, all down the data tree  

	N  int    `inject:"+"`  // inject field
	S  string `inject:"+"`
	D  Data   `inject:"*"`
	NL []int  `inject:"+"`

	Map     map[string]interface{} `inject:"+"`
	DataPtr *Data                  `inject:"*"`

	SI SI `inject:"+"`
}

It is also possible to inject arguments of a function using the Invoke method.