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Version: 6.x

How-to: Trees

Example 1

Task

We have a set of books associated with certain categories.

CLASS Category 'Category';
name 'Name' = DATA ISTRING[50] (Category);

CLASS Book 'Book';
name 'Name' = DATA ISTRING[50] (Book);
category 'Category' = DATA Category (Book);

We need to build a form with a tree, where the category is shown above and the product is shown below.

Solution

FORM books 'Books'
TREE cb c = Category, b = Book
PROPERTIES name(c), name(b)
FILTERS category(b) == c
;

Example 2

Task

Similar to Example 1, except that each category has a parent in the hierarchy.

parent 'Parent' = DATA Category (Category);

We need to build a form with a tree, where the categories will be displayed as hierarchy.

Solution

FORM categories 'Categories'
TREE categories c = Category PARENT parent(c)
PROPERTIES(c) name
;

Example 3

Task

Similar to Example 2.

We need to create a form with a category tree, so that the books that belong to the current category and all its subcategories are shown to the right.

Solution

level 'Level' (Category child, Category parent) = RECURSION 1l IF child IS Category AND parent == child
STEP 2l IF parent == parent($parent) MATERIALIZED;

FORM categoryBooks 'Books by category'
TREE categories c = Category PARENT parent(c)
PROPERTIES(c) name

OBJECTS b = Book
PROPERTIES(b) name
FILTERS level(category(b), c)
;

DESIGN categoryBooks {
NEW pane FIRST {
fill = 1;
horizontal = TRUE;
MOVE BOX(TREE categories);
MOVE BOX(b);
}
}