How to use GET parameters (parameters in the URL)?

Pages are generated by services.

Funcrions to create services using GET HTTP method take two mandatory parameters: ~path and ~get_params.

path

This argument is a list of string, corresponding to the URL where your page service can be found.

For example, if you want your page to be accessed via this URL:

http://website.com/a/b/c

You must provide this path:

~path:["a";"b";"c"]

This parameter can also be an empty list. It means that the service page will be accessed via this URL:

http://website.com/

get_params

Eliom chooses the service automatically w.r.t. this path and parameter given (among other criteria). It decodes parameters automatically and checks their types.

Description of parameters (names and types) is done using module Eliom_parameter. We recommend to open this module (at the beginning of your file, or locally).

Syntax for several parameters

No parameter

~get_params:unit

One parameter

~get_params:(int "id")

More parameters

~get_params:(string "name" ** int "age" ** bool "graduate")

Types of parameters

Common types: string, int, int32, float, bool
Some other types: optional values, any parameter, list, your own type.

See more information on parameters in Eliom manual and API documentation of module Eliom_parameter.

Get these parameters

On service registration, parameters can be retrieved as a parameter of the function:

Example.register ~service:the_service
    (fun parameters () -> ...)

No parameter

(fun () () -> ...)

One parameter

(fun a () -> ...)

Several parameters

Operator ** is left associative:

(fun (a, (b, (c, d)))) () -> ...)

Parameters in the path

Sometimes you may want to take parameters from the path, for example to improve readability of URLs. E.g. http://blah.com/archive/2014/2/ or http://blah.com/user/toto/.

To do that, add a parameter of type suffix in get_params:

~get_params:(suffix (string "username"))

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