Compatibility between external component and deployed application

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Overview
Taking into account the update of a component in a deployed application
1. Recompiling the project that is using the component (recommended)
2. Distributing the .WDK file directly
Compatibility modes
Definition
Backward compatibility
Forward compatibility

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Compatibility between external component and deployed application

Overview

The evolutions of a component can be of several kinds:

addition of features, modification of features,
various corrections, ...

This help page presents:

How do I take into account the update of a component in a deployed application.
The different compatibility modes of a component: backward and forward compatibility.

Taking into account the update of a component in a deployed application

Two methods can be used to update a component in an application deployed on the end-user computers:

Recompiling the project that is using the component (recommended)
Distributing the .WDK file directly

1. Recompiling the project that is using the component (recommended)

Recompile the application that is using the component and redistribute the application (with the component).

In this case, no version problem or compatibility problem will occur.

The recompilation is required in the following cases:

New functions have been added to the component and they must be taken into account by the application.
The parameters of some procedures have been modified.
Incompatibility between the new version of the component and the earlier versions of the component.
...

2. Distributing the .WDK file directly

Provide an upgraded version of component (.WDK file) to the end users without recompiling the project.

This method can be used in the following cases:

The new version is used to correct the problems of an earlier version.
New features have been added into the component but they are not required to run the application.

Compatibility modes

Definition

The management of compatibility is linked to the component versions. Indeed, if modifications have been made to the component, the applications that use the component in deployment may encounter runtime problems if they are not synchronized with this component.

The management of the compatibility is an important step when distributing a component.

Two types of compatibility exist:

the backward compatibility: the component version (.WDK file) used to compile the applications that use this component must always be greater than or equal to the version currently used. This compatibility is automatically managed by WINDEV. If the version of the distributed component is less than the one used by the applications, these applications will not work.
the forward compatibility: using a new version of a component with the projects compiled with an earlier version can be forbidden. Therefore, the projects must be recompiled in order to use the new component version.

Backward compatibility

WINDEV always checks the version number of the components to make sure that the version of the component used in deployment is greater than or equal to the one used in the development project.

For example:

The project was compiled with the version 1.00C of a component.
The version 1.00C is the reference version. Which means that the applications that use this component will operate only if the component version is greater than or equal to the reference version.
- First case: The applications deployed on the end-user computers use a version of the component (.WDK file) less than version 1.00C. An error will occur when loading these applications.
- Second case: The applications deployed on the end-user computers will operate if they use the expected component version.
- Third case: The applications deployed on the end-user computer will operate if the version of the component is greater than the expected one (only if the new version is used to fix bugs).

Forward compatibility

WINDEV automatically detects the incompatibilities between two versions of the same component when this component is generated. If differences are found, WINDEV proposes to modify the "number of the last compatible version". This number is the version number from which the applications that use the component will be allowed to operate.

For example:

A project that used the version 1.00C of the component has not been recompiled with the new version 1.00E of this component.
A component is distributed in version 1.00E.
- First case: the component was modified to fix bugs only. When generating the component, the "number of the last compatible version" has not been modified.
  In order for the applications to operate properly, there is no need to recompile the projects with the new component version. The component (.WDK file) can be distributed to the end users directly.
- Second case: the component was modified in order to add a parameter to a procedure for instance. When generating the component, the "number of last compatible version" was modified.
  In order for the applications to operate properly, the projects must be recompiled with the new component version. Otherwise, the applications will refuse to operate in order to avoid problems due to potential incompatibility with the new component version.