iOS Framework Overview

iOS is an operating system that executes on iphone, IPod touch, or ipad, previously known as iphone Os,ios and Mac OS X have a common infrastructure and underlying technology. However, iOS is designed to be based on the features of mobile devices, so it is slightly different from Mac OS X systems, such as support for multi-touch and acceleration sensors.

Take a look down at the iOS framework for a brief introduction:
The system architecture of IOS is divided into four tiers: the core OS layer, the core service layer, the media layer, and the Cocoa touch layer. Shows a comparison of Mac OS X and iOS system architecture levels.

From here we can find that the system architecture level of Mac OS X and iOS is different from the top level, the cocoa framework is replaced by the Cocoa Touch, so developing an iOS application is similar to developing a Mac OS X program, so let's take a closer look at what each layer contains.
In fact, iOS is UNIX-based, so we can totally trust this operating system, knowing that from the stability of the system it is much better than the products of other operating systems.
The layer at the top of the iOS system architecture is the core operating system layer, which contains memory management, file systems, power management, and some other operating system tasks. It is capable of interacting directly with hardware devices. The core operating system layer contains the following components:
os X Kernelmach 3.0bsd
socketspower Mgmtfile System
keychaincertificatessecurity
bonjour
The second tier is the core service layer, which we can use to access some of the iOS services. It contains the following components:
collectionsaddress booknetworking
file Accesssqlitecore Location
net servicesthreadingpreferences
url Utilities
The third layer is the media layer, through which we can use a variety of media files in the application, for audio and video recording, graphic drawing, as well as the production of the basis of animation effect. It contains the following components:
core Audioopenglaudio Mixing
audio Recordingvideo Playbackjpg,png,tiff
pdfquartzcore Animation
opengl ES
The topmost layer is the touch layer, which provides a variety of useful frameworks for our application development, and most of it is about the user interface, which is essentially responsible for the user's touch interaction on the iOS device. It contains the following components:
multi-touch Eventscore Motioncamera
view Hierarchylocalizationalerts
web viewsimage Pickermulti-touch Controls
Much of the technology in the cocoa Touch layer is based on the Objective-c language. The Objective-c language provides support for iOS like collections, file management, network operations, and more. Like the Uikit framework, it provides a variety of visual components for applications, such as form (Window), view, and button components (UIButton). Other frameworks in the Cocoa touch layer are also very useful for our development in the application, such as access to the user's communication function framework, the framework for obtaining photo information, the framework for hardware support such as acceleration sensors and three-dimensional gyroscopes.

iOS Framework Introduction

What is a framework? It is essentially a software library that helps us complete a variety of specific functions.
The application projects we wrote started from the cocoa touch layer, in detail, starting with the Uikit framework. When there are some special functions that need to be used in the process of tapping the code, we should start by looking for the corresponding frame from the top technology of the frame, and use the technology of the lower layer only when the superstructure cannot be solved. In fact, the top-level framework already covers most of the features we need.
Table 1-1 lists some of the frequently used iOS SDK frameworks.

iOS Framework Overview