In daily life, we see that everything is connected to one another. For example, leaves are connected to branches and branches are connected to a tree. The life of leaves depends on their attachment to the branches. Similarly, a human has a heart, a car uses fuel, and a cat is an animal. In programming, every class is connected to another related class with different relationships. There are two major types of relationships in this case.
has-arelationshipis-arealtioship
It means to keep the object of one class in another class. It is called container-ship or possession. In a "has-a" relationship, we can say that a parent class has a child class. The child class can be totally dependent or independent on the creation or destruction of the main class. This relationship is further divided into two more subtypes.
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It is always a good practice to pass the aggregated object as
constto avoid accidentally changing its properties and methods by using its public methods. This can be done by usingconstkeyword with them, to ensure that the aggregated object is not modified. This helps in keeping the integrity of the object and reducing the chances of bugs in the code. -
From an
abstractionstandpoint, it is primarily recommended to use references and aggregation. In the main function, we simply pass the aggregated object's name without the use of the&sign. This way, the user is not exposed to the concepts of aggregation and composition. -
"It is important to note that the
has-arelationship type cannot be determined solely based on data types. For example, just because you seeArray *arr;does not necessarily mean that it is an aggregation relationship. It could also be used for dynamic composition, as inarr = new Array[5]. To truly determine the relationship, one should examine the class constructor to see if addresses are being copied or used for dynamic purposes."