Module: Constraint::Helper

Included in:
Shell, Shell
Defined in:
lib/constraint.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Instance Attribute Details

#constaint_descriptions ⇒ Object (readonly)

A hash of constraint constaint_descriptions.



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# File 'lib/constraint.rb', line 76

def constaint_descriptions
  @constaint_descriptions
end

#constaint_handlers ⇒ Object (readonly)

An array of constraint handlers



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# File 'lib/constraint.rb', line 78

def constaint_handlers
  @constaint_handlers
end

#constraint_attributes ⇒ Object (readonly)

An array of additional attributes that should be copied when replicating a shell



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# File 'lib/constraint.rb', line 81

def constraint_attributes
  @constraint_attributes
end

#constraints ⇒ Object (readonly)

The current class’s/object’s head constraint.



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# File 'lib/constraint.rb', line 74

def constraints
  @constraints
end

Instance Method Details

#and_constraint(name, desc = nil, &block) ⇒ Object

Define an SingleConstraint. This and all previous constraints have to succeed.

name

This constraint’s name

description

Optional constraint description

block

The constraint that must evaluate to true in order for this constraint to succeed



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# File 'lib/constraint.rb', line 109

def and_constraint(name, desc=nil, &block)
    describe_constraint(name, desc)
    @constraints = @constraints.dup
    @constraints << SingleConstraint.new(self, name, desc, &block)
end

#constraint_attr(name, val) ⇒ Object 



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# File 'lib/constraint.rb', line 145

def constraint_attr(name, val)
    (@constraint_attributes = @constraint_attributes.dup) << name
    instance_eval %{
        class << self
            attr_accessor :#{name}
        end
        attr_accessor :#{name}
    }
    instance_variable_set("@#{name}", val)
end

#log_constraint_exception(exception) ⇒ Object

If $VERBOSE is set, print the exception to $stderr.



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# File 'lib/constraint.rb', line 116

def log_constraint_exception(exception)
    if $VERBOSE
        $stderr.puts exception
    end
end

#on_constraint_violation(*names, &block) ⇒ Object

Define a new constraint handler. The block takes a continuation as its first argument. If the amendment of the object isn’t successful, the handler must throw an Constraint::Violation exception.

Example:

enum = EvenInteger.new(2)
enum.and_constraint('LT10') {|enum, n| n < 10}
enum.on_constraint_violation('LT10') do |o, n|
    n > 10 ? 10 : 0
end
*names

The constraints names

block

The handler (argument: object)



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# File 'lib/constraint.rb', line 137

def on_constraint_violation(*names, &block)
    @constaint_handlers = @constaint_handlers.dup
    names.each do |name|
        @constaint_handlers[name] ||= []
        @constaint_handlers[name] << block
    end
end

#or_constraint(name, desc = nil, &block) ⇒ Object

Define an OrConstraint. Either this or the previous constraint have to succeed.

name

This constraint’s name

description

Optional constraint description

block

The constraint that must evaluate to true in order for this constraint to succeed



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# File 'lib/constraint.rb', line 87

def or_constraint(name, desc=nil, &block)
    describe_constraint(name, desc)
    @constraints = @constraints.dup
    constraint   = SingleConstraint.new(self, name, desc, &block)
    if @constraints.empty?
        @constraints << constraint
    else
        last = @constraints.last
        case last
        when OrConstraint
            last << constraint
        else
            @constraints[-1] = OrConstraint.new([last, constraint])
        end
    end
end

#replicate_constraints(predecessor) ⇒ Object

Copy needed class/object variables.



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# File 'lib/constraint.rb', line 157

def replicate_constraints(predecessor)
    @constaint_descriptions = predecessor.constaint_descriptions
    @constaint_handlers     = predecessor.constaint_handlers
    @constraints            = predecessor.constraints
    for name in (@constraint_attributes = predecessor.constraint_attributes)
        nname = "@#{name}"
        instance_variable_set(nname, predecessor.instance_variable_get(nname))
    end
end