CODEWITHSUNDEEP
go
Rusfearuth
Rusfearuth

Reputation: 3261

How to import package by path from string in Go?

I have a string with name of package (like "my/package/test") and I wanna import that and call some function from package.

Something like this:

func init() {
  var pkg string = "test/my/pkg"
  import pkg
  pkg.Test()
}

PS. Thanks for help

Upvotes: 4

Views: 5245

Answers (2)

user811773
user811773

Reputation:

The Go language does not allow what you mentioned in your example. This is a conscious choice. In my opinion, the reason behind this choice has to do with compiler performance and ease of code understanding by the machine. This for example enables tools such as gofix that can partially fix Go code without need for user intervention.

It also enables a programmer to clearly see all of the statically imported packages used by the program.

See also the grammar rules for source file organization in the Go language specification.

In relation to dynamically loading packages at run-time: Go has no support for loading packages at run-time. A future Go run-time might implement this feature (for example, it is occasionally being requested in messages in the golang-nuts mailing list), but the current state is that there is no support for this feature.

Upvotes: 6

tux21b
tux21b

Reputation: 94639

That's not possible in Go. The linker has to know the dependencies at compile-time, your string (and the init-function) are however evaluated at run-time. Also note, that parts of your programs which are not used, i.e. everything which isn't referred explicitly, wont even be part of the final binary - so reflection is not possible either.

If you need something like that, you have to manage the mapping on your own. You can for example use a global map in one package and use the init functions in the other packages to register the relevant functions, by adding them to the map. After that, you can use the map to do your look-ups dynamically.

Take a look at the http package for example. In a fictional blog package you might use the blog.init() function to register a couple of http handlers using the http.HandleFunc(pattern, handler) function. The main package then might call http.ListenAndServe() which looks up the right handlers at run-time.

Upvotes: 3

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