Create a route for dispatching on URL

Source: R/route.R

The Route class is used to encapsulate a single URL dispatch, that is, chose a single handler from a range based on a URL path. A handler will be called with a request, response, and keys argument as well as any additional arguments passed on to dispatch().

Details

The path will strip the query string prior to assignment of the handler, can contain wildcards, and can be parameterised using the : prefix. If there are multiple matches of the request path the most specific will be chosen. Specificity is based on number of elements (most), number of parameters (least), and number of wildcards (least), in that order. Parameter values will be available in the keys argument passed to the handler, e.g. a path of /user/:user_id will provide list(user_id = 123) for a dispatch on /user/123 in the keys argument.

Handlers are only called for their side-effects and are expected to return either TRUE or FALSE indicating whether additional routes in a RouteStack should be called, e.g. if a handler is returning FALSE all further processing of the request will be terminated and the response will be passed along in its current state. Thus, the intend of the handlers is to modify the request and response objects, in place. All calls to handlers will be wrapped in try() and if an exception is raised the response code will be set to 500 with the body of the response being the error message. Further processing of the request will be terminated. If a different error handling scheme is wanted it must be implemented within the handler (the standard approach is chosen to avoid handler errors resulting in a server crash).

A handler is referencing a specific HTTP method (get, post, etc.) but can also reference all to indicate that it should match all types of requests. Handlers referencing all have lower precedence than those referencing specific methods, so will only be called if a match is not found within the handlers of the specific method.

Initialization

A new 'Route'-object is initialized using the new() method on the generator:

Usage

route <- Route$new(...)

Arguments

...Handlers to add up front. Must be in the form of named lists where the names corresponds to paths and the elements are the handlers. The name of the argument itself defines the method to listen on (see examples)

Methods

The following methods are accessible in a Route object:

add_handler(method, path, handler)

Add a handler to the specified method and path. The special method 'all' will allow the handler to match all http request methods. The path is a URL path consisting of strings, parameters (strings prefixed with :), and wildcards (*), separated by /. A wildcard will match anything and is thus not restricted to a single path element (i.e. it will span multiple / if possible). The handler must be a function containing the arguments request, response, keys, and ..., and must return either TRUE or FALSE. The request argument will be a reqres::Request object and the response argument will be a reqres::Response object matching the current exchange. The keys argument will be a named list with the value of all matched parameters from the path. Any additional argument passed on to the dispatch method will be avaiable as well. This method will override an existing handler with the same method and path.

remove_handler(method, path)

Removes the handler assigned to the specified method and path. If no handler have been assigned it will throw a warning.

get_handler(method, path)

Returns a handler already assigned to the specified method and path. If no handler have been assigned it will throw a warning.

remap_handlers(.f)

Allows you to loop through all added handlers and reassings them at will. A function with the parameters method, path, and handler must be provided which is responsible for reassigning the handler given in the arguments. If the function does not reassign the handler, then the handler is removed.

dispatch(request, ...)

Based on a reqres::Request object the route will find the correct handler and call it with the correct arguments. Anything passed in with ... will be passed along to the handler.

See also

RouteStack for binding multiple routes sequentially

Methods

Public methods

Method new()

Usage

Route$new(...)

Method print()

Usage

Route$print(...)

Method add_handler()

Usage

Route$add_handler(method, path, handler)

Method remove_handler()

Usage

Route$remove_handler(method, path)

Method get_handler()

Usage

Route$get_handler(method, path)

Method remap_handlers()

Usage

Route$remap_handlers(.f)

Method dispatch()

Usage

Route$dispatch(request, ...)

Method clone()

The objects of this class are cloneable with this method.

Usage

Route$clone(deep = FALSE)

Arguments

deep

Whether to make a deep clone.

Examples

# Initialise an empty route
route <- Route$new()

# Initialise a route with handlers assigned
route <- Route$new(
  all = list(
    '/*' = function(request, response, keys, ...) {
      message('Request recieved')
      TRUE
    }
  )
)

# Remove it again
route$remove_handler('all', '/*')