Class: Middleware::Builder

Inherits:
Object
  • Object
show all
Defined in:
lib/middleware/builder.rb

Overview

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 |b|
  b.use A
  b.use B
end

# Call the middleware
app.call(7)

Instance Method Summary collapse

Constructor Details

#initialize(opts = nil) { ... } ⇒ Builder

Initializes the builder. An optional block can be passed which will either yield the builder or be evaluated in the context of the instance.

Example:

Builder.new do |b|
  b.use A
  b.use B
end

Builder.new do
  use A
  use B
end

Parameters:

  • opts (Hash) (defaults to: nil) —

    Options hash

Options Hash (opts):

  • :runner_class (Class) —

    The class to wrap the middleware stack in which knows how to run them.

Yields:

  • Evaluated in this instance which allows you to use methods

    like #use and such.



40
41
42
43
44
45
46
47
48
49
50
51
 
# File 'lib/middleware/builder.rb', line 40

def initialize(opts=nil, &block)
  opts ||= {}
  @runner_class = opts[:runner_class] || Runner

  if block_given?
    if block.arity == 1
      yield self
    else
      instance_eval(&block)
    end
  end
end

Instance Method Details

#call(env = nil) ⇒ Object

Runs the builder stack with the given environment.



128
129
130
 
# File 'lib/middleware/builder.rb', line 128

def call(env=nil)
  to_app.call(env)
end

#delete(index) ⇒ Object

Deletes the given middleware object or index



122
123
124
125
 
# File 'lib/middleware/builder.rb', line 122

def delete(index)
  index = self.index(index) unless index.is_a?(Integer)
  stack.delete_at(index)
end

#flatten ⇒ Object

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.



56
57
58
59
60
 
# File 'lib/middleware/builder.rb', line 56

def flatten
  lambda do |env|
    self.call(env)
  end
end

#insert(index, middleware, *args, &block) ⇒ Object Also known as: insert_before

Inserts a middleware at the given index or directly before the given middleware object.



80
81
82
83
84
 
# File 'lib/middleware/builder.rb', line 80

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

#insert_after(index, middleware, *args, &block) ⇒ Object

Inserts a middleware after the given index or middleware object.



89
90
91
92
93
 
# File 'lib/middleware/builder.rb', line 89

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

#insert_after_each(middleware, *args, &block) ⇒ Object

Inserts a middleware after each middleware object



103
104
105
106
107
 
# File 'lib/middleware/builder.rb', line 103

def insert_after_each(middleware, *args, &block)
  self.stack = stack.reduce([]) do |carry, item|
    carry.push(item, [middleware, args, block])
  end
end

#insert_before_each(middleware, *args, &block) ⇒ Object

Inserts a middleware before each middleware object



96
97
98
99
100
 
# File 'lib/middleware/builder.rb', line 96

def insert_before_each(middleware, *args, &block)
  self.stack = stack.reduce([]) do |carry, item|
    carry.push([middleware, args, block], item)
  end
end

#inspect ⇒ Object 



132
133
134
135
136
 
# File 'lib/middleware/builder.rb', line 132

def inspect
  "[" + stack.reduce([]) { |carry, middleware|
    carry << "#{middleware[0].class.name}(#{middleware[1].join(', ')})"
  }.join(', ') + "]"
end

#replace(index, middleware, *args, &block) ⇒ Object

Replaces the given middleware object or index with the new middleware.



111
112
113
114
115
116
117
118
119
 
# File 'lib/middleware/builder.rb', line 111

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

#use(middleware, *args, &block) ⇒ Object

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.

Parameters:

  • middleware (Class) —

    The middleware class



67
68
69
70
71
72
73
74
75
76
 
# File 'lib/middleware/builder.rb', line 67

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