It's time to write your first generic function in Go!
Take a look at the print_test.go file in this folder. You'll find the following test:
func TestPrintAnythingTo_PrintsInputToSuppliedWriter(t *testing.T) {
t.Parallel()
buf := &bytes.Buffer{}
print.PrintAnythingTo[string](buf, "Hello, world")
want := "Hello, world\n"
got := buf.String()
if !cmp.Equal(want, got) {
t.Error(cmp.Diff(want, got))
}
}First, run the go mod tidy command to download the necessary modules for this test. Once that's completed, you're ready to start the exercise.
Run the test using your editor, or the go test command. You'll find right now the test doesn't compile, because the required function doesn't exist:
undefined: print.PrintAnythingTo
Remember, you'll need at least Go version 1.18 to be able to use generics, including running this test and implementing the function to make it pass. That's because we're using some new syntax that doesn't exist in Go version 1.17 and earlier.
If you try to compile this code with a version of Go that doesn't support generics, you'll get a rather confusing additional error message:
type string is not an expression
So if you see this, you need to upgrade your Go.
To make this test compile, you'll need to define a function in the print package named PrintAnythingTo that takes one parameter of type io.Writer, and another value that's of some unspecified type.
To make the test pass, that function will need to write the supplied value to the supplied writer. It's up to you how to do this, but you might like to use fmt.Fprintln.
The necessary go.mod and print.go files are already set up for you. All you need to do is edit print.go and add the PrintAnythingTo function, then run the test again.
The main point of this exercise is to get you up and running writing generics in Go, and to get some practice declaring functions that take type parameters. When the test passes, you're done, so you can move on to the next exercise.
If you get stuck, you can take a look at my suggested answer in Solution 2.1.