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Columns - page of object PmDataTable

Description:
Definition of table columns.
Configuration items of one column:
Name Column name. The name must be unique in this table. The column can then be referred to with column number or with column name. See method Item
Data typeData type sloupce. This data type will be preserved in the column variable and the written values will be converted into this data type. The only exception is the Variant data type which means that the variable keeps the last written value including the data type.
 
Identifier of row:

In the first column it is possible to select data type Identifier. Then the values in the first column are used as row identifiers. Identifier must be unique in this column. The row can then be referred to with row number or row identifier. See method Item.

NoteComment of the current column. It is relevant only in the development environment.
Read onlyIf checked then the varibale in this column can be written only once. See "Read only" columns.
Note:
When starting the application, the table has columns that are defined here. Columns can be changed dynamically (See method InsertCol, RemoveCol). So the setting on this page can be regarded as the initial setting of the columns.
 
Maximum number of columns depends on PROMOTIC Runtime License and is: PmRtProf: 65535, PmRtStandard: 50000, PmRtLite: 100, PmRtFree: 30
 
"Read only" columns:

Each cell of the table is counted into the application size for the purpose of licencing. But if a column of table in PmDataTable object is marked as "Read only" then the cells in this column are not counted into application size. This allows application designers to use such object for storing non-changing configuration values while the number of licenced variables is kept low. From the functional point of view this means that columns marked "Read only" can be written only once. Limitations of individual methods of the PmDataTable caused by "Read only" columns are explained in remark.

Each cell is empty at the beginning. The cell is considered empty also if it contains numeric value 0 or an emty string "". New value can be written into such cell. After writing a non-zero value into the "Read only" column the cell is "locked". "Locked cell" becomes a constant and cannot be written again. Other still "unlocked" cells can be written into as needed. Methods that write into multiple cells simultaneously will write the values only into "unlocked cells" while the content of "locked" cells remains unchanged.

If any cell is locked in "Read only" column by writing non-empty value the the whole structure of the table is locked. Then it is no longer possible to add or remove rows or columns or change the structure of the table. The structure and dimensions of the table must be defined and modified before writing first non-empty value into a cell in "Read only" column.

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