指针引用未存储在我的go程序的结构中

Question

I am new to go-lang and I try to figure out how to work properly with structs and dependency injection. I am a bit stuck because I am not able to properly store a reference to another struct.

Here's my method that generates a CommandController. There is a valid reference to iris.Application.

func ProvideCommandController(application *iris.Application, commandRepository command.CommandRepository) (*interfaces.CommandController, error) {
commandController := interfaces.CommandController{}
commandController.Init(application, commandRepository)
commandController.Start()
return &commandController, nil

}

The struct looks like this:

type CommandController struct {
    commandRepository command.CommandRepository
    app   *iris.Application
}

func (c CommandController) Init(app *iris.Application, repository command.CommandRepository) {
    c.app = app
    c.commandRepository = repository
}

func (c CommandController) Start() {
    c.app.Get("/command", c.readAll)
    c.app.Get("/command/{id:string}/execute", c.executeCommand)

    c.app.Run(iris.Addr(":8080"))
}

When the ProvideCommandController function gets executed I can debug and observe that all references look good. Unfortunately, commandController.Start()fails because of c.app is nil.

What piece of understanding do I miss? Somehow, the stored reference get's deleted between the Init and the Start function call.

Thanks in advance :)

Answer 1

Change

func (c CommandController) Init(app *iris.Application, repository command.CommandRepository)

to

func (c *CommandController) Init(app *iris.Application, repository command.CommandRepository)

since Init receives c by value in your version, any changes it makes to c don't appear outside of the Init method.