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Register Factory Functions
In Parsely, you can register a factory function to provide more control and customization when creating service instances. A factory function differs from a constructor function because it allows you to pass additional parameters to configure the service creation process.
Instead of directly registering a constructor function that returns a service instance, you register a factory function that returns another function. This returned function is then used to create the actual service instances.
Here’s a detailed look at how to register and use a factory function:
Suppose you want to create a Greeter service where the salutation can be customized. You can use a factory function to achieve this. Here’s how you would define and register a factory function:
package internal
import "fmt"
type Greeter interface {
SayHello(name string, polite bool)
}
type greeter struct {
salutation string
}
func (g *greeter) SayHello(name string, polite bool) {
if polite {
fmt.Printf("Good day, %s!\n", name)
} else {
fmt.Printf("%s, %s\n", g.salutation, name)
}
}
func NewGreeterFactory(salutation string) func() Greeter {
return func() Greeter {
return &greeter{salutation: salutation}
}
}This is how you use it:
func main() {
registry := registration.NewServiceRegistry()
_ = registration.RegisterTransient(registry, internal.NewGreeterFactory("Hi"))
resolver := resolving.NewResolver(registry)
scope := resolving.NewScopedContext(context.Background())
greeter, _ := resolving.ResolveRequiredService[internal.Greeter](resolver, scope)
const polite = false
greeter.SayHello("John", polite)
}