How to Handle Optional URL Parameters in Gorilla Mux?

How to Handle Optional URL Variables with Gorilla Mux

Creating routes with optional URL variables can be achieved in Gorilla Mux library. Let's explore how to do it:

Current Setup and Issue:

The provided code defines a route that requires an integer variable id in the URL, but not all scenarios may necessitate an id. The goal is to make the route accept both cases: with and without the id variable.

Solution:

To achieve this, register the handler twice:

r.HandleFunc("/view", MakeHandler(ViewHandler))
r.HandleFunc("/view/{id:[0-9]+}", MakeHandler(ViewHandler))

By registering the handler with the path /view without any parameters, it allows the route to work even when there is no id.

Handling Vars:

When retrieving variables from the request, it's essential to check for the presence of the id variable:

vars := mux.Vars(r)
id, ok := vars["id"]
if !ok {
    // Directory listing or equivalent logic
    return
}
// Specific view logic

If id is not present in the request (i.e., /view was requested), the ok variable will be false, and you can handle it appropriately (e.g., display a directory listing). Otherwise, the id value is available for use in the specific view handler.

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