On Sunday, 28 February 2021 at 03:03:17 UTC Deiter wrote: > The example uses a “short assignment” statement, so it’s not obvious what > “concrete” type c.StdoutPipe() returns >
You can't tell, and indeed it might not return any concrete type at all (it may return nil). Given stdout, err := cmd.StdoutPipe() then the types of those variables are exactly the types of the values returned by StdoutPipe, i.e. stdout is of type "io.ReadCloser" and err is of type "error". Both of these happen to be interface types. The important thing to note is that a variable can have a static type which is "an interface type". At runtime, it can hold any value of any concrete type which implements that interface - or "nil", which is the zero value of an interface type. If the interface value is not nil, then the concrete value is boxed in such a way that you can invoke the interface methods. However, given rPipe, _ := io.Pipe() then the type of variable rPipe is "*PipeReader", which is a pointer to a concrete type <https://golang.org/pkg/io/#PipeReader>. The only thing you can assign to variable rPipe is a value of type *PipeReader. Somewhat confusingly, pointer values can also be "nil", but a nil pointer value is not the same thing as a nil interface value. -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/golang-nuts/e85ba460-2b04-4357-acbf-561db8c48959n%40googlegroups.com.
