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;
type = SPLITH;
MOVE BOX(TREE categories);
MOVE BOX(b);
}
}