Binding properties pattern

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The Binding properties pattern is combining multiple observers to force properties in different objects to be synchronized or coordinated in some way. This pattern was first described as a technique by Victor Porton.[1][2] This pattern comes under concurrency patterns.

Comparison with aspect-oriented implementation[edit]

As an alternative to the aspect-oriented implementation of mutual properties, property binding can be proposed. In LibPropC++ C++ library it is implemented too.[3]

Some weakness in the LibPropC++ (with property binding):

  1. Its use is not transparent as it requires to be declared necessary object attributes as properties and appropriate accessor methods must be provided
  2. Binding of attributes in LibPropC++ is not designed to replace method calls
  3. The library does not maintain an interaction history.[3]

Implementation[edit]

There are two types of binding. One-way binding should be applied when one of the properties is read-only. In other cases, two-way binding must be applied.[2][3]

Infinite loops can be eliminated by blocking the signal, or comparing the assigned value with the property value before assignment, or eliminating unnecessary assignments.[2][3]

Binding properties of different types can be achieved through Type Conversions.[2][3]

Binding properties with transformations can be achieved through reducing the transformation function to the problem of binding properties, and the function can be imaginary consider as Type Conversions.[2][3]

Procedural programming
Object-oriented programming
Singals/event programming
Components with properties
binding properties together

[2]

Resulting Context[edit]

Properties are being kept synchronized automatically. Between library calls they always have the values expressed by the EqualityConstraints.[3]

Deficiencies[edit]

Property changes watching mechanism acquires some resources.[3]

Sample Code[edit]

Code sketch for one-way binding may look like as follows:

bind_multiple_one_way(src_obj, src_prop, dst_objs[], dst_props[])
{
  for (i, j) in (dst_objs, dst_props)
  {
    bind_properties_one_way(src_obj, src_prop, i, j);
  }
}

[2]

Two-way binding can be expressed as follows (in C++):

// In this pseudo-code are not taken into the account initial values assignments
bind_two_way(prop1, prop2)
{
  bind(prop1, prop2);
  bind(prop2, prop1);
}

[3]

Accomplishing the binding (i.e. connecting the property change notification in an event handler) may be like as follows:

on_property_change(src_prop, dst_prop)
{
  block_signal(src_obj, on_property_change);
  dst_prop := src_prop;
  unblock_signal(src_obj, on_property_change);
}

[3]

See also[edit]

References[edit]

  1. ^ "Binding Properties". Cunningham & Cunningham. Cunningham & Cunningham. Retrieved 4 February 2015. 
  2. ^ a b c d e f g Porton, V. "Binding together Properties of Objects: Extreme Code Software". Ex-code. Ex-code. Retrieved 1 September 2008. 
  3. ^ a b c d e f g h i j Evermann, J., The Association Construct in Conceptual Modelling - An Analysis Using the Bunge Ontological Model, Wellington, New Zealand: School of Information Management, Victoria University