The
form is used to create and manage data classes. These are a new kind of object
in the entity-relationship model, on which object-oriented methods can be used.
More information: -> Data classes.
Attention! The integration of object-oriented components with the help of data classes will follow a new approach in future versions of DataView. For this reason it is recommended to refrain from creating new data classes in the modeling phase and to use only the classical model objects entity, entity type, relation, and link. Data classes that have already been created are still supported for reasons of compatibility.
Field Assignment |
1:n/n:1 Relationships |
Triggers |
Methods |
Base Classes |
Where Qualification |
Class Name | a data class' name |
Object Title | a data class' title |
Type | a data class' display type (table or view) |
Comments | comments about a data class |
Create Object | adds an instance of the object to the database |
Delete Object | deletes a data class |
Create procedures | writes stored procedures to the database |
Delete Procedures | deletes stored procedures from the database |
Data Class Access | opens a data class' Access form |
attribute | master attribute for data classes (T_TABLE) |
type, entry | string, entry required |
max. no. of characters | 13 |
selection tool | no |
multilingual field | no |
The class name identifies the data class uniquely within the application's data model. A database object instantiated from a data class need not be explicitly named, as it automatically receives the name of the data class.
Object Title
attribute
master attribute for data classes (T_TABLE)
type, entry
string, entry optional
max. no. of characters
20
selection tool
no
multilingual field
no
The title is used in error messages.
Note!
You should always give your objects a title. If you don't, error messages will only contain the object's key, and you won't be able to find the object in a Search mask.
Type
attribute
master attribute for data classes (T_TABLE)
type, entry
string, entry required
max. no. of characters
1
selection tool
all existing types
multilingual field
no
The display type determines how a data class is displayed in the database.
More information:
-> Table formats,
-> View formats
Comments
attribute
master attribute for data classes(T_TABLE)
type, entry
string, entry oprtional
max. no. of characters
255
selection tool
no
multilingual field
yes
Create Object
Before creating the master table or view, you first need to create the table or view fields in the Field Assignment sublist.
Attention! Do not use the function while the application is running. Always ensure that no other users are using the tables first.
DataView automatically checks to see if this table exists, and creates one if necessary. If it exists, DataView will adjust it, either directly in the database (for minor modifications) or by starting an Export/Import with the binary loader (for major modifications). Before starting the loader, it makes a security check.
If the loader is used, DataView automatically does the following (you can follow the process in the Messages Console):
If DataView is unable to create the new table because of definition errors, the loader file remains in the tmp folder. After correcting the definitions, the function can be called again.
Note! When altering (setting) the Non-Null flag (to zero), ensure that there are entries for every possible user record in the modified table column. Otherwise DataView will be unable to load the loader file into the new table.
Note! DataView always uses the binary loader, even if the ASCII loader is selected in the LOADER default.
If you modify definitions for views as opposed to tables, Create Table/View will not modify the view in the database, but delete it completely and create a new view.
If you modify an existing data class, you need to update it in the data base with Create Object only if you have modifies field assignments, associations or WHERE qualifications. You can modify trigger functions or method calls without recreating the class in the database.
More information:
-> Deleting or modifying objects
Delete Object
Attention! Do not use the function while the application is running. Always ensure that no other users are using the tables first.
When a table or view is deleted, the repository retains all the class' descriptive data.
More information:
-> Deleting or modifying objects
Create Procedures
Delete Procedures
Data Class Access
This function extends the scope of the standard Access function. Access privileges apply not only to the data class object, but also to all lists and forms which refer to it.