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POLA-POLA
PERANCANGAN (PPP)
Structural pattern: Composite
Bahan Kuliah PPP - Composite pattern | Tri A. Kurniawan, S.T, M.T, Ph.D 2/27
Tujuan perkuliahan
• Memahami structural pattern: Composite
Bahan Kuliah PPP - Composite pattern | Tri A. Kurniawan, S.T, M.T, Ph.D 3/27
Intent• Compose objects into tree structures to
represent part-whole hierarchies
• Composite lets clients treat individual
objects and compositions of objects
uniformly
Bahan Kuliah PPP - Composite pattern | Tri A. Kurniawan, S.T, M.T, Ph.D 4/27
Motivation
Bahan Kuliah PPP - Composite pattern | Tri A. Kurniawan, S.T, M.T, Ph.D 5/27
Motivation (1)
Bahan Kuliah PPP - Composite pattern | Tri A. Kurniawan, S.T, M.T, Ph.D 6/27
Applicability
• You want to represent part-whole
hierarchies of objects
• You want clients to be able to ignore the
difference between compositions of objects
and individual objects clients will treat all
objects in the composite structure
uniformly
Bahan Kuliah PPP - Composite pattern | Tri A. Kurniawan, S.T, M.T, Ph.D 7/27
Structure
Bahan Kuliah PPP - Composite pattern | Tri A. Kurniawan, S.T, M.T, Ph.D 8/27
Bahan Kuliah PPP - Composite pattern | Tri A. Kurniawan, S.T, M.T, Ph.D 9/27
Participants
• Component– declares the interface for objects in the composition
– implements default behavior for the interface common to all classes, as appropriate
– declares an interface for accessing and managing its child components
– (optional) defines an interface for accessing a component's parent in the recursive structure, and implements it if that's appropriate
• Leaf– represents leaf objects in the composition A leaf has no
children
– defines behavior for primitive objects in the composition
Bahan Kuliah PPP - Composite pattern | Tri A. Kurniawan, S.T, M.T, Ph.D 10/27
Participants (1)
• Composite– defines behavior for components having
children
– stores child components
– implements child-related operations in the Component interface
• Client– manipulates objects in the composition through
the Component interface
Bahan Kuliah PPP - Composite pattern | Tri A. Kurniawan, S.T, M.T, Ph.D 11/27
Collaborations
• Client use the Component class interface to interact with objects in the composite structure:
– If the recipient is a Leaf, then the request is handled directly
– If not, then it usually forwards requests to its child components, possibly performing additional operations before and/or after forwarding
Bahan Kuliah PPP - Composite pattern | Tri A. Kurniawan, S.T, M.T, Ph.D 12/27
Consequences
• Defines class hierarchies consisting of primitive objects and composite objects
• Makes the client simple do not know whether a leaf or a composite to deal with
• Makes it easier to add new kinds of components Client do not need to change
• (disadvantage) Can make your design overly general
Bahan Kuliah PPP - Composite pattern | Tri A. Kurniawan, S.T, M.T, Ph.D 13/27
Sample code
Bahan Kuliah PPP - Composite pattern | Tri A. Kurniawan, S.T, M.T, Ph.D 14/27
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Wait a sec….
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