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What is key-value observing?
Overview. Key-value observing is a Cocoa programming pattern you use to notify objects about changes to properties of other objects. It’s useful for communicating changes between logically separated parts of your app—such as between models and views.
What is key-value coding and key-value observing?
Key-value coding is a mechanism enabled by the NSKeyValueCoding informal protocol that objects adopt to provide indirect access to their properties. When an object is key-value coding compliant, its properties are addressable via string parameters through a concise, uniform messaging interface.
What is key-value observing Swift?
Key-value observing is a mechanism that enables an object to be notified directly when a property of another object changes. It is a mode of communication between objects in applications designed in conformance with the Model-View-Controller design pattern.
What is KVO key-value observation )?
KVO, which stands for Key-Value Observing, is one of the techniques for observing the program state changes available in Objective-C and Swift. The concept is simple: when we have an object with some instance variables, KVO allows other objects to establish surveillance on changes for any of those instance variables.
What is KVO compliant?
It is also possible to implement compliance manually. KVO Compliance describes the difference between automatic and manual key-value observing, and how to implement both. KVO’s primary benefit is that you don’t have to implement your own scheme to send notifications every time a property changes.
What is the difference between Key Value Observing and Key Value Coding?
To observe a property using KVO you would identify to property with a string; i.e., using KVC. Therefore, the observable object must be KVC compliant. Key Value Coding is simply accessing a property of an object through a string instead of the literal syntax.
What is difference between KVC and KVO?
KVC stands for Key-Value Coding. It’s a mechanism by which an object’s properties can be accessed using string’s at runtime rather than having to statically know the property names at development time. KVO stands for Key-Value Observing and allows a controller or class to observe changes to a property value.
What is the relationship between view and MVC?
In this way UI is a combination of the view and the controller. MVC is about separation of concerns, not about relationships. Business Logic should be in the model. The controller is only for interacting with the user. Typically the view fetches the necessary information from the model.
How does MVC work in Ruby on rails?
Another part of MVC is how the model, view and controller interact. In this case all the views and controllers observe the model. When the model changes, the views react. This is very different from MVC as made popular by Ruby on Rails, where the controller is responsible for preparing and loading the view.
What’s the relationship between MVC and business logic?
MVC is about separation of concerns, not about relationships. Business Logic should be in the model. The controller is only for interacting with the user. Typically the view fetches the necessary information from the model. When using passive views, objects (from the model) are passed from the controller.
How is MVC used in the present time?
The View observes and responds to changes in model. The model is the Domain Model rather than an individual recordset or entity. How MVC is commonly used in the present time differs from the original MVC pattern as it was coined by Martin Fowler. He based this pattern in Smalltalk.