Class: Handshake::MethodContract

Inherits:
ProcContract show all
Defined in:
lib/handshake.rb

Overview

Class representing method contracts. Not for external use.

Instance Attribute Summary collapse

Attributes inherited from ProcContract

#accepts, #returns

Instance Method Summary collapse

Methods inherited from ProcContract

#accepts_varargs?, #check_returns!, #signature=

Constructor Details

#initialize(method_name) ⇒ MethodContract

Returns a new instance of MethodContract.



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# File 'lib/handshake.rb', line 395

def initialize(method_name)
  @method_name = method_name
  @preconditions, @postconditions = [], []
  @accepts, @returns = [], []
end

Instance Attribute Details

#block_contract ⇒ Object (readonly)

Returns the value of attribute block_contract.



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# File 'lib/handshake.rb', line 393

def block_contract
  @block_contract
end

#postconditions ⇒ Object

:nodoc:



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# File 'lib/handshake.rb', line 392

def postconditions
  @postconditions
end

#preconditions ⇒ Object

:nodoc:



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# File 'lib/handshake.rb', line 392

def preconditions
  @preconditions
end

Instance Method Details

#accepts=(args) ⇒ Object

If the last argument is a Block, handle it as a special case. We do this to ensure that there’s no conflict with any real arguments which may accept Procs.



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# File 'lib/handshake.rb', line 455

def accepts=(args)
  if args.last == Block # Transform into a ProcContract
    args.pop
    @block_contract = ProcContract.new
    @block_contract.accepts = ClauseMethods::ANYTHING
    @block_contract.returns = ClauseMethods::ANYTHING        
  elsif args.last.is_a?(ProcContract)
    @block_contract = args.pop
  end

  if args.find_all {|o| o.is_a? Array}.length > 1
    raise ContractError, "Cannot define more than one expected variable argument"
  end
  super(args)
end

#check_accepts!(*args, &block) ⇒ Object 



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# File 'lib/handshake.rb', line 401

def check_accepts!(*args, &block)
  super(*args, &block)
  if expects_block?
    check_equivalence!(block, Proc)
  end
end

#check_conditions!(o, args, conditions) ⇒ Object

Checks the given conditions against the object, passing the given args into the block. Throws :contract if any fail or if an exception is raised. Because of the need to evaluate the condition in the context of the object itself, a temporary method called bound_condition_passes? is defined on the object, using the block associated with the condition. TODO Is there a better way to evaluate an arbitary block in a particular binding? There must be.



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# File 'lib/handshake.rb', line 436

def check_conditions!(o, args, conditions)
  conditions.each do |condition|
    o.class.instance_eval do
      define_method(:bound_condition_passes?, &(condition.block))
    end
    begin
      o.bound_condition_passes?(*args)
    rescue Test::Unit::AssertionFailedError => afe
      throw :contract, AssertionFailed.new(afe.message)
    rescue Exception => e
      throw :contract, e
    end
    o.class.send(:remove_method, :bound_condition_passes?)
  end
end

#check_post!(o, *args) ⇒ Object

Checks the postconditions of this contract against the given object and return values. Any assertions thrown are re-raised as Handshake::AssertionViolation errors.



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# File 'lib/handshake.rb', line 419

def check_post!(o, *args)
  check_conditions!(o, args, @postconditions)
end

#check_pre!(o, *args) ⇒ Object

Checks the preconditions of this contract against the given object and arugment values. Any assertions thrown are re-raised as Handshake::AssertionFailed errors.



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# File 'lib/handshake.rb', line 426

def check_pre!(o, *args)
  check_conditions!(o, args, @preconditions)
end

#defined? ⇒ Boolean

Returns true only if this MethodContract has been set up to check for one or more contract conditions.

Returns:

  • (Boolean) 


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# File 'lib/handshake.rb', line 410

def defined?
  [ preconditions, postconditions, accepts, returns ].any? do |ary|
    not ary.empty?
  end
end

#expects_block? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/handshake.rb', line 471

def expects_block?
  not @block_contract.nil?
end