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Routing

When a client (web browser) points to a path (e.g.: /about) a request is made to the server (GET in this case), ambiorix then looks through the handlers for a matching path and runs the respective handler function (\(req, res)). This function should return a response (using the res object) or a future (see asynchronous programming).

library(ambiorix)

app <- Ambiorix$new()

app$get("/", \(req, res){
res$text("Home!")
})

app$get("/about", \(req, res){
res$send("About me!")
})

app$start()

In the app above when the client (browser) points to /about the server goes over the handlers in the order they are specified looking for a match, the first / does not match, the second /about does; it therefore runs that handler which sends a response back.

Handler

The handler function used for every route must take 2 arguments: the request, and the response. The first holds data on the request that is made to the server, which contains many things but importantly includes parameters and the parsed query string. You can learn more about these in the parameters and query section.

library(ambiorix)

app <- Ambiorix$new()

app$get("/?name", \(req, res){
msg <- htmltools::h1("Hello", req$query$name)
res$send(msg)
})

app$get("/users/:id", \(req, res){
msg <- sprintf("This is user id: #%s", req$params$id)
res$text(msg)
})

app$start()

Forward

Since routes are checked in a certain order one can use forward to indicate that the next route should be checked instead.

library(ambiorix)

app <- Ambiorix$new()

app$get("/next", \(req, res){
forward()
})

app$get("/next", \(req, res){
res$send("Hello")
})

app$start()

If no route match the requested path then ambiorix runs the 404/not_found handler, see not found.

Routing is crucial to ambiorix, therefore it also comes with a router to better structure complex routing for large applications.