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An interface contains definitions for a group of related functionalities that a non-abstract class or a struct must implement. An interface may define static methods, which must have an implementation. Beginning with C# , an interface may define a default implementation for members. An interface may not declare instance data such as fields, auto-implemented properties, or property-like events. Interfaces form a contract between the class and the outside world, and this contract is enforced at build time by the compiler. If your class claims to implement an interface, all methods defined by that interface must appear in its source code before the class will successfully compile.
An interface contains definitions for a group of related functionalities that a non-abstract class or a struct must implement. An interface may define static methods, which must have an implementation. Beginning with C 8. An interface may not declare instance data such as fields, auto-implemented properties, or property-like events. By using interfaces, you can, for example, include behavior from multiple sources in a class.
That capability is important in C because the language doesn't support multiple inheritance of classes. In addition, you must use an interface if you want to simulate inheritance for structs, because they can't actually inherit from another struct or class.
You define an interface by using the interface keyword as the following example shows. The name of an interface must be a valid C identifier name. By convention, interface names how to draw a roof in autocad with a capital I.
A class or struct can implement multiple interfaces, but a class can only inherit from a single class. Interfaces can contain instance methods, properties, events, indexers, or any combination of those four member types.
Interfaces may contain static constructors, fields, constants, or operators. For links to examples, see Related Sections. An interface can't contain instance fields, instance constructors, or finalizers. Interface members are public by default, and you can explicitly specify accessibility modifiers, such as publicprotectedinternalprivateprotected internalor private protected. A private member must have a default implementation. To implement an interface member, the corresponding member of the implementing class must be public, non-static, and have the same name and signature as the interface member.
When a class or struct implements an interface, the class or struct must provide an implementation for all of the members that the interface declares but doesn't provide a default implementation for. However, if a base class implements an interface, any class that's derived from the base class inherits that implementation.
The implementing class, Carmust provide an implementation of the Equals method. Properties and indexers of a class can define extra accessors for a property or indexer that's defined in an interface. For example, an interface might declare a property that has a get accessor. The class that implements the interface can declare the same property with both a get and set accessor. However, if the property or indexer uses explicit implementation, the accessors must match.
For more information about explicit implementation, see Explicit Interface Implementation and Interface Properties. Interfaces can inherit from one or more interfaces. The derived interface inherits the members from its base interfaces. A class that implements a derived interface must implement all members in the derived interface, including all members of the derived interface's base interfaces.
That class may be implicitly converted to the derived interface or any of its base interfaces. A class might include an interface multiple times through base classes that it inherits or through what is dc voltage source that other interfaces inherit. However, the class can provide an implementation of an interface only one time and only if the class declares the interface as part of the definition of the class class ClassName : InterfaceName.
If the interface is inherited because you inherited a base class that implements the interface, the base class provides the implementation of the members of the interface. However, the derived class can reimplement any virtual interface members instead of using the inherited implementation.
When interfaces declare a default implementation of a method, any class implementing that interface inherits that implementation. Implementations defined in interfaces are virtual and the implementing class may override that implementation.
A base class can also implement interface members by using virtual members. In that case, a derived class can change the interface behavior by overriding the virtual members. For more information about virtual members, see Polymorphism.
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Within the Java programming language, an interface is a type, just as a class is a type. Like a class, an interface defines methods. Unlike a class, an interface never implements methods; instead, classes that implement the interface implement the methods defined by the interface. A . In object oriented programming, an interface generally defines the set of methods (or messages) that an instance of a class that has that interface could respond to. What adds to the confusion is that in some languages, like Java, there is an actual interface with its language specific semantics. Interface members are by default abstract and public; An interface cannot contain a constructor (as it cannot be used to create objects) Why And When To Use Interfaces? 1) To achieve security - hide certain details and only show the important details of an object (interface).
An interface is a description of the actions that an object can do In Object Oriented Programming, an Interface is a description of all functions that an object must have in order to be an "X". The purpose of interfaces is to allow the computer to enforce these properties and to know that an object of TYPE T whatever the interface is must have functions called X,Y,Z, etc.
For example, say we have a car class and a scooter class and a truck class. An interface has a very simple syntax that looks very much like a class definition Interfaces are placed in their own files which have the same name as the interface are Capitalized and end with the familiar language extension e.
The following interface would be placed in a "Vehicle. Here is an example of the Vehicle interface referred to above only a partial definition. An interface is about actions that are allowed, not about data or implementation of those actions.
The keyword public is not placed in front of the function prototypes. By definition, all functions listed in an interface must be public functions. There is no code after the function prototype.
To tell the computer that a new class that you are writing will fulfill all the requirements implement all the functions of an interface, you must use the keyword implements in the same location where you can use the keyword extends. Remember: While all functions in the interface must be implemented in the class, you can also create any other functions you want for that class.
What is the power of the interface? The power is that once we have a number of classes which implement the interface, from some point of view, they are equivalent. For example, say we want to create a Car and a Truck, but all our program wants to do is "start" them and "drive" them. To our program's "point of view" they are just Vehicles. Below are examples showing how we would write the code without interfaces, with interfaces, and then with a generic arrays of "Vehicles".
The final example above shows the concept of Polymorphism. Polymorphism is the idea that an compile time coding time we don't know and often can't know what the actual type of object inside a variable will be. In the vehicles array above, we don't know if vehicles[i] is a car, truck, bicycle, etc. In computer languages without polymorphism, we wouldn't be able to do anything with these objects.
With polymorphism, the computer remembers what each is and when we say: "item. Polymorphism save the programmer a lot of time and effort in coding up "exceptional" conditions. The computer does the work for us, a remembering what each object really is, and then b at run time, invoking the actual function associated with the current object.
Sometimes, you will want to use a function specific to an underlying type. How can I tell this to the computer. Here is the proper code. You should strive not to use the as key word except when absolutely necessary. When we don't use it, we have the assurance of the computer that our types are correct. When we do use it, all we have is the programmers assurance, and programmers are often wrong.
They allow the programmer to be more abstract when referencing objects for example, var vehicle : Vehicle, can reference any car, truck, etc This occurs at "program time". When the vehicle. This occurs at "run time". They require the programmer to create specific functions that are expected in an implementing class when it implements an Interface.
Again, this allows all objects in a "set" of like objects to be treated based on the "high level" type of the set, rather than on the specific type of the individual object. Interfaces An interface is a description of the actions that an object can do The syntax of an Interface An interface has a very simple syntax that looks very much like a class definition Implementing an Interface To tell the computer that a new class that you are writing will fulfill all the requirements implement all the functions of an interface, you must use the keyword implements in the same location where you can use the keyword extends.
Here is an example of a Car Class which implements the Vehicle definition. Polymorphism applied to Interfaces What is the power of the interface? Normally we would have to create separate vehicles. But because the are all vehicles vehicles.