module Roda::RodaPlugins::SymbolMatchers

The symbol_matchers plugin allows you do define custom regexps to use for specific symbols. For example, if you have a route such as:

r.on :username do |username|
  # ...
end

By default this will match all nonempty segments. However, if your usernames must be 6-20 characters, and can only contain a-z and 0-9, you can do:

plugin :symbol_matchers
symbol_matcher :username, /([a-z0-9]{6,20})/

Then the route will only if the path is /foobar123, but not if it is /foo, /FooBar123, or /foobar_123.

By default, this plugin sets up the following symbol matchers:

:d	/(\d+)/, a decimal segment
:rest	/(.*)/, all remaining characters, if any
:w	/(\w+)/, an alphanumeric segment

If the placeholder_string_matchers plugin is loaded, this feature also applies to placeholders in strings, so the following:

r.on "users/:username" do |username|
  # ...
end

Would match /users/foobar123, but not /users/foo, /users/FooBar123, or /users/foobar_123.

If using this plugin with the params_capturing plugin, this plugin should be loaded first.

You can provide a block when calling symbol_matcher, and it will be called for all matches to allow for type conversion:

symbol_matcher(:date, /(\d\d\d\d)-(\d\d)-(\d\d)/) do |y, m, d|
  Date.new(y.to_i, m.to_i, d.to_i)
end

route do |r|
  r.on :date do |date|
    # date is an instance of Date
  end
end

If you have a segment match the passed regexp, but decide during block processing that you do not want to treat it as a match, you can have the block return nil or false. This is useful if you want to make sure you are using valid data:

symbol_matcher(:date, /(\d\d\d\d)-(\d\d)-(\d\d)/) do |y, m, d|
  y = y.to_i
  m = m.to_i
  d = d.to_i
  Date.new(y, m, d) if Date.valid_date?(y, m, d)
end

You can have the block return an array to yield multiple captures.

The second argument to symbol_matcher can be a symbol already registered as a symbol matcher. This can DRY up code that wants a conversion performed by an existing class matcher or to use the same regexp:

symbol_matcher :employee_id, :d do |id|
  id.to_i
end
symbol_matcher :employee, :employee_id do |id|
  Employee[id]
end

With the above example, the :d matcher matches only decimal strings, but yields them as string. The registered :employee_id matcher converts the decimal string to an integer. The registered :employee matcher builds on that and uses the integer to lookup the related employee. If there is no employee with that id, then the :employee matcher will not match.

If using the class_matchers plugin, you can provide a recognized class matcher as the second argument to symbol_matcher, and it will work in a similar manner:

symbol_matcher :employee, Integer do |id|
  Employee[id]
end

Blocks passed to the symbol matchers plugin are evaluated in route block context.

If providing a block to the symbol_matchers plugin, the symbol may not work with the params_capturing plugin. Note that the use of symbol matchers inside strings when using the placeholder_string_matchers plugin only uses the regexp, it does not respect the conversion blocks registered with the symbols.

Methods

Public Class

1. configure
2. load_dependencies

Classes and Modules

1. Roda::RodaPlugins::SymbolMatchers::ClassMethods
2. Roda::RodaPlugins::SymbolMatchers::RequestMethods