The purpose of these articles is to help both those who are new in the use of the tool and those who have used it for quite a while but do not have enough time to test the new functionalities and at the same time eliminate the various obstacles you are faced with when using the tool or when taking your projects to different production environments.

Through this effort we seek to receive comments and suggestions of topics of interest for the community in order to gain understanding of the powerful GeneXus tool.

Today's article provides a simple, clear and concise explanation of Structured Data Types (SDT). In the first part, the basic operation of SDTs is shown and in the second part, there is a detailed description of the work with SDT collections.

What is SDT?
SDT is the definition of a customized structure. When you need to use this structure in a GeneXus object, you may define a variable with the required SDT type. This means the SDT resides in the memory.

SDTs operate like objects in other languages.

If, for example, you were in C#, the SDT definition would be the "Class", while when using it you would be working with the class instance.

It is worth mentioning that the most significant difference between SDTs and objects is that SDTs do not have their own functionality. It is not possible to define methods, among other more subtle differences.

Let's say we have the "PCliAdd" process with the following code:

Rules:
parm( in:CliNom, in:CliApe, in:CliDir, in:CliTel, in:CliCiu, in:CliPais, in:CliCP);

Source:
new
CliId = PGetNumber.Udp("CLI")
endnew

From any customer addition process you would call the previous process as follows:

PCliAdd.Call( "Aldo", "Rmido", "18 de Julio 1830", "4136260", "Montevideo", "Uruguay", 11200)

With an SDT, it would be solved in the following way:

&Cliente.CliNom = "Aldo"
&Cliente.CliApe = "Rmido"
&Cliente.CliDir = "18 de Julio 1830"
&Cliente.CliTel = "4136260"
&Cliente.CliCiu = "Montevideo"
&Cliente.CliPais = "Uruguay"
&Cliente.CliCP = 11200
PCliAdd.Call(sdtCliente)

Accordingly, the procedure "PCliAdd" would change as follows:

Rules:
parm( in:&Cliente);

Source:

new
CliId = PGetNumber.Udp("CLI")
CliNom = &Cliente.CliNom
CliApe = &Cliente.CliApe
Elidir = &Cliente.CliDir
CliTel = &Cliente.CliTel
CliCiu = &Cliente.CliCiu
CliPais = &Cliente.CliPais
CliCP = &Cliente.CliCP
endnew

As you see with the SDT the call to the "PCliAdd" procedure is highly simplified and you can view the information of the parameters you are loading, and therefore the call is not as confusing as the previous one.

Likewise, when you need new parameters in your process, you do not need to modify the "parm" rule; instead, you modify the SDT instead. This is an added value because it allows managing "optional parameters".

With this example, we intend to show its use in processes with large quantity of parameters, which sometimes confuse the code.

Creating your first SDT

Creating an SDT is very simple, and to continue with the previous examples, we will use the example of the "sdtCliente".

1) Go to "Object/New Object" menu option.

2) Select "Structured Data Type" and write "sdtCliente" in the name. You may also write a description if you want.

3) At this point, you create the attributes as if you were in a transaction. You may add a new field by pressing enter and indicating your data type.

Of course, you may also base those attributes on domains defined in your KB.

E.g.: CliNom - Character(32).

To speed up the insertion of attributes in the SDT, you have the option of selecting attributes directly ("Insert Atributes...") from the "contextual menu" of the SDT (right button) or copying the structure directly from a transaction ("Copy structure from...").

Implementing your SDT

In order to use the SDT you have previously created, you must create an "sdtCliente" type variable in a GeneXus functional object (Transaction, Procedure, Report, etc.).

To access the SDT attributes you must use the ".". A very clear example of this is presented in the first part of our article.

For example, if you define the variable "&Cliente" of the "sdtCliente" type and you want to access the name attribute you will do it as follows:

&Cliente.CliNom = "Jose"
msg(&Cliente.CliNom)
Import and Export to XML

A very interesting SDT feature is the possibility of exporting them from and importing them to XML format.

You may see an example of their use in the web environment. Let's say you have a security SDT with the following structure:

sdtSession
+UsrLogin - Character(20)
+UsrHorIni - DateTime

Using SDT toXML function, you may save the result in a cookie and when you need to perform a security check, you may obtain the SDT again from the cookie using the XML function.

Example:

Login procedure