class Middleware::Builder
This provides a DSL for building up a stack of middlewares.
This code is based heavily off of `Rack::Builder` and `ActionDispatch::MiddlewareStack` in Rack and Rails, respectively.
# Usage
Building a middleware stack is very easy:
app = Middleware::Builder.new do use A use B end # Call the middleware app.call(7)
Public Class Methods
Initializes the builder. An optional block can be passed which will be evaluated in the context of the instance.
Example:
Builder.new do use A use B end
@param [Hash] opts Options hash @option opts [Class] :runner_class The class to wrap the middleware stack
in which knows how to run them.
@yield [] Evaluated in this instance which allows you to use methods
like {#use} and such.
# File lib/middleware/builder.rb, line 35 def initialize(opts=nil, &block) opts ||= {} @runner_class = opts[:runner_class] || Runner @reuse_instance = opts[:reuse_instance] instance_eval(&block) if block_given? end
Public Instance Methods
Runs the builder stack with the given environment.
# File lib/middleware/builder.rb, line 103 def call(env=nil) if @reuse_instance runner_instance.call(env) else to_app.call(env) end end
Deletes the given middleware object or index
# File lib/middleware/builder.rb, line 97 def delete(index) index = self.index(index) unless index.is_a?(Integer) stack.delete_at(index) end
Returns a mergeable version of the builder. If `use` is called with the return value of this method, then the stack will merge, instead of being treated as a separate single middleware.
# File lib/middleware/builder.rb, line 45 def flatten lambda do |env| self.call(env) end end
Inserts a middleware at the given index or directly before the given middleware object.
# File lib/middleware/builder.rb, line 69 def insert(index, middleware, *args, &block) index = self.index(index) unless index.is_a?(Integer) raise "no such middleware to insert before: #{index.inspect}" unless index stack.insert(index, [middleware, args, block]) end
Inserts a middleware after the given index or middleware object.
# File lib/middleware/builder.rb, line 78 def insert_after(index, middleware, *args, &block) index = self.index(index) unless index.is_a?(Integer) raise "no such middleware to insert after: #{index.inspect}" unless index insert(index + 1, middleware, *args, &block) end
Replaces the given middleware object or index with the new middleware.
# File lib/middleware/builder.rb, line 86 def replace(index, middleware, *args, &block) if index.is_a?(Integer) delete(index) insert(index, middleware, *args, &block) else insert_before(index, middleware, *args, &block) delete(index) end end
Adds a middleware class to the middleware stack. Any additional args and a block, if given, are saved and passed to the initializer of the middleware.
@param [Class] middleware The middleware class
# File lib/middleware/builder.rb, line 56 def use(middleware, *args, &block) if middleware.kind_of?(Builder) # Merge in the other builder's stack into our own self.stack.concat(middleware.stack) else self.stack << [middleware, args, block] end self end
Protected Instance Methods
Returns the numeric index for the given middleware object.
@param [Object] object The item to find the index for @return [Integer]
# File lib/middleware/builder.rb, line 117 def index(object) stack.each_with_index do |item, i| return i if item[0] == object end nil end
# File lib/middleware/builder.rb, line 140 def runner_instance @runner_instance ||= to_app end
Returns the current stack of middlewares. You probably won't need to use this directly, and it's recommended that you don't.
@return [Array]
# File lib/middleware/builder.rb, line 129 def stack @stack ||= [] end
Converts the builder stack to a runnable action sequence.
@return [Object] A callable object
# File lib/middleware/builder.rb, line 136 def to_app @runner_class.new(stack.dup) end