Sfairadora
- Reference Guide
Data Type Document Section
Individual items in the Data Type section correspond with items in the Data
section of the same name. If you create a new item in the Data Type section, an item
of the same name is automatically created also in the Data
section. The Data
section is used to enter the value of the item, whereas the Data Type
section is used to specify its type.
For example, if you select the Integer number (
Int)
type in the Data Type section, the respective item in the Data
section is represented by a line
editor, in which you can enter a number. Similarly, if you select the table
type in the Data Type section, containing First_name and Last_name
columns of the String (String)
type, the respective item in the Data
section is a table
with these two columns, in which you can enter a list of {First_name, Last_name}
pairs.
The object name of the item and the data
type editor are displayed in the right pane of the main window (or in a separate window
if you double-click the item). The name must be an identifier.
When you edit the data type, the changes are immediately applied to the actual data in the Data
section; you can observe this behavior by opening the respective Data
section item in a separate window by a double click so that it is displayed together with the editor
of its type. If the type is incorrectly specified (e.g. two columns have the same name, etc.), the item
type in the Data
section is not changed and an error message is displayed in the status
line.
Preservation of Data When Changing Its Type
Sfairadora endeavors to preserve as much as possible of the already existing data in any
item whose type is being changed. This is straightforward when an item or a table column are being renamed.
When the data type is changed, Sfairadora performs a data
type conversion : if you change, for example, the type of a column in a table from String
to Integer number, then string values representing numbers are converted to numbers
and all other values are replaced by 0 (or left missing if the column is defined as optional).
You can perform even more complicated operations that still preserve your data. For example, if you create
a new table column by coping the definition of an existing column, values in the table instance are also
copied from the original column to the new one. Furthermore, data is preserved in the following situation:
1.
Create a new item (i.e. new column) in the data type section of an existing table and set its type to
“Table”.
2.
Press the details button – you will see a list of columns of the newly created
subordinate table.
3.
Copy one item from the parent table to the new table – the instances of the subordinate tables
will contain one row each with the value from the source column that has been copied.
Another useful feature is the option to change the type from computed
to basic – the computed values are thus fixed.
Data Type Lock
If you need to perform a more complex data type manipulation, it may be undesirable to have the partial
changes of type immediately applied to the actual data. In some situations you will need to change the
type by a series of changes and apply these changes to the data at the end, all at once. This is achieved
by the button with the image of a padlock
located to the right of the “Data Type”
title. The button works as a switch – if it is in the “locked” mode, data type modifications
are not applied to the data. When you switch the button to “unlocked” again, all changes
are applied to the data. This lock locks data type and view type at once.
located to the right of the “Data Type”
title. The button works as a switch – if it is in the “locked” mode, data type modifications
are not applied to the data. When you switch the button to “unlocked” again, all changes
are applied to the data. This lock locks data type and view type at once.