Cocoa入门指南：探索苹果开发环境的关键概念与设计模式

需积分: 10 117 浏览量更新于2024-07-29 收藏 4.39MB PDF 举报

“Cocoa Fundamentals Guide 是一份针对开发者的新手指南，旨在帮助初学者理解并适应Cocoa这一开发环境。这份指南介绍了Cocoa的技术特点、工具、基本概念、术语、架构以及设计模式，以助于开发者快速入门。” Cocoa是Apple开发的一个用于创建 macOS 和 iOS 应用程序的强大框架。它基于Objective-C编程语言，提供了丰富的类库和工具，使得开发者可以构建功能丰富的应用程序。Cocoa Fundamentals Guide 深入浅出地讲解了Cocoa的核心概念，对于想要进入Apple平台开发的程序员来说是一份极其宝贵的资源。 1. **Cocoa的基础** - **Objective-C**: Cocoa是基于Objective-C的，这是一种面向对象的语言，结合了Smalltalk的消息传递机制和C语言的强类型系统。学习Cocoa首先需要掌握Objective-C的基本语法，如消息传递、类、协议等。 2. **Cocoa的主要组件** - **Foundation框架**: 提供了基础数据结构、线程管理、I/O操作等功能，是Cocoa的基础。 - **AppKit (macOS) / UIKit (iOS)**: 提供了用户界面元素和事件处理机制，如窗口、视图、按钮等，是构建应用界面的关键部分。 3. **设计模式** - **Model-View-Controller (MVC)**: MVC是Cocoa主要的设计模式，将应用程序分为模型、视图和控制器三个部分，各司其职，提高代码的可维护性和可扩展性。 - **Key-Value Coding (KVC) 和 Key-Value Observing (KVO)**: 这是Cocoa中的数据绑定技术，允许动态访问和观察对象属性，简化了对象间的交互。 4. **Cocoa Bindings** - Cocoa Bindings是Cocoa提供的一种机制，它简化了MVC架构中模型与视图之间的数据同步，通过声明式编程减少了代码量。 5. **Cocoa Touch (iOS)**: 针对iOS设备的用户界面和交互方式，包括手势识别、屏幕适配等特性，是iOS应用开发的重要组成部分。 6. **Core Data** - Core Data是Apple提供的数据管理框架，它简化了数据库操作，支持模型对象的持久化，方便数据的存储和检索。 7. **内存管理** - 在Objective-C中，Cocoa使用引用计数进行内存管理，理解 retain, release, autorelease 等概念至关重要，后来的iOS引入了ARC（Automatic Reference Counting），自动处理内存管理。 8. **Interface Builder** - Interface Builder是Cocoa开发中的可视化工具，允许开发者拖放UI元素并连接到代码，加速界面设计和开发过程。 9. **事件响应** - Cocoa中的事件驱动模型，包括事件循环和事件委托，使得开发者能够处理用户的输入。 10. **文档系统** - Apple的文档系统是开发者的重要参考资料，包括头文件、编程指南和示例代码，有助于深入理解Cocoa的各个部分。 Cocoa Fundamentals Guide 是一个全面介绍Cocoa的起点，它涵盖了从语言基础到高级特性的广泛内容，是开发者踏上Apple平台开发之路的必备指南。通过深入学习和实践，开发者可以逐渐熟悉并掌握这个强大的框架，从而创造出优秀的macOS和iOS应用程序。

● Core Graphics. The Cocoa drawing and imaging classes are (quite naturally) closely based on the Core

Graphics framework, which implements Quartz and the window server.

● Launch Services. The NSWorkspace class exposes the underlying capabilities of Launch Services. Cocoa

also uses the application-registration feature of Launch Services to get the icons associated with

applications and documents.

Note: The intent of this architectural overview is not to itemize every relationship that Cocoa has to other

parts of Mac OS X. Instead, it surveys the more interesting ones in order to give you a general idea of the

architectural context of the framework.

Apple has carefully designed Cocoa so that some of its programmatic interfaces give access to the capabilities

of underlying technologies that applications typically need. But if you require some capability that is not

exposed through the programmatic interfaces of Cocoa, or if you need some finer control of what happens

in your application, you may be able to use an underlying framework directly. (A prime example is Core

Graphics; by calling its functions or those of OpenGL, your code can draw more complex and nuanced images

than is possible with the Cocoa drawing methods.) Fortunately, using these lower-level frameworks is not a

problem because the programmatic interfaces of most dependent frameworks are written in standard ANSI

C, of which Objective-C language is a superset.

Further Reading: Mac OS X Technology Overview gives an overview of the frameworks, services, technologies,

and other components of Mac OS X. Apple Human Interface Guidelines specifies how the Aqua human interface

should appear and behave.

How Cocoa Fits into iOS

The application-framework layer of iOS is called Cocoa Touch. Although the iOS infrastructure on which

Cocoa Touch depends is similar to that for Cocoa in Mac OS X, there are some significant differences. Compare

Figure 1-2, which depicts the architectural setting of iOS, to the diagram in Figure 1-1 (page 15). The iOS

diagram also shows the software supporting its platform as a series of layers going from a Core OS foundation

to a set of application frameworks, the most critical (for applications) being the UIKit framework. As in the

Mac OS X diagram, the iOS diagram has middle layers consisting of core-services frameworks and graphics

and media frameworks and libraries. Here also, a component at one layer often has dependencies on the

layer beneath it.

Figure 1-2 Cocoa in the architecture of iOS

Core OS

Core Services

Media

Cocoa Touch

Application

Foundation

UIKit

Core Frameworks

The Cocoa Environment

CHAPTER 1

What Is Cocoa?

Generally, the system libraries and frameworks of iOS that ultimately support UIKit are a subset of the libraries

and frameworks in Mac OS X. For example, there is no Carbon application environment in iOS, there is no

command-line access (the BSD environment in Darwin), there are no printing frameworks and services, and

QuickTime is absent from the platform. However, because of the nature of the devices supported by iOS,

there are some frameworks, both public and private, that are specific to iOS.

The following summarizes some of the frameworks found at each layer of the iOS stack, starting from the

foundation layer.

● Core OS. This level contains the kernel, the file system, networking infrastructure, security, power

management, and a number of device drivers. It also has the libSystem library, which supports the

POSIX/BSD 4.4/C99 API specifications and includes system-level APIs for many services.

● Core Services. The frameworks in this layer provide core services, such as string manipulation, collection

management, networking, URL utilities, contact management, and preferences. They also provide services

based on hardware features of a device, such as the GPS, compass, accelerometer, and gyroscope.

Examples of frameworks in this layer are Core Location, Core Motion, and System Configuration.

This layer includes both Foundation and Core Foundation, frameworks that provide abstractions for

common data types such as strings and collections. The Core Frameworks layer also contains Core Data,

a framework for object graph management and object persistence.

● Media. The frameworks and services in this layer depend on the Core Services layer and provide graphical

and multimedia services to the Cocoa Touch layer. They include Core Graphics, Core Text, OpenGL ES,

Core Animation, AVFoundation, Core Audio, and video playback.

● Cocoa Touch. The frameworks in this layer directly support applications based in iOS. They include

frameworks such as Game Kit, Map Kit, and iAd.

The Cocoa Touch layer and the Core Services layer each has an Objective-C framework that is especially

important for developing applications for iOS. These are the core Cocoa frameworks in iOS:

● UIKit. This framework provides the objects an application displays in its user interface and defines the

structure for application behavior, including event handling and drawing. For a description of UIKit, see

“UIKit (iOS)” (page 44).

● Foundation. This framework defines the basic behavior of objects, establishes mechanisms for their

management, and provides objects for primitive data types, collections, and operating-system services.

Foundation is essentially an object-oriented version of the Core Foundation framework; see

“Foundation” (page 30) for a discussion of the Foundation framework.

Notes: This document uses “Cocoa” generically when referring to things that are common between the

platforms. When it is necessary to say something specific about Cocoa on a given platform, it uses a phrase

such as “Cocoa in Mac OS X.”

As with Cocoa in Mac OS X, the programmatic interfaces of Cocoa in iOS give your applications access to the

capabilities of underlying technologies. Usually there is a Foundation or UIKit method or function that can

tap into a lower-level framework to do what you want. But, as with Cocoa in Mac OS X, if you require some

capability that is not exposed through a Cocoa API, or if you need some finer control of what happens in

your application, you may choose to use an underlying framework directly. For example, UIKit uses the WebKit

to draw text and publishes some methods for drawing text; however, you may decide to use Core Text to

The Cocoa Environment 17

CHAPTER 1

What Is Cocoa?

draw text because that gives you the control you need for text layout and font management. Again, using

these lower-level frameworks is not a problem because the programmatic interfaces of most dependent

frameworks are written in standard ANSI C, of which the Objective-C language is a superset.

Further Reading: To learn more about the frameworks, services, and other aspects of the iOS platform, see

iOS Technology Overview.

Features of a Cocoa Application

In Mac OS X it is possible to create a Cocoa application without adding a single line of code. You make a new

Cocoa application project using Xcode and then build the project. That’s it. Of course, this application won’t

do much, or at least much that’s interesting. But this extremely simple application still launches when

double-clicked, displays its icon in the Dock, displays its menus and window (titled “Window”), hides itself

on command, behaves nicely with other running applications, and quits on command. You can move, resize,

minimize, and close the window. You can even print the emptiness contained by the window.

You can do the same with an iOS application. Create a project in Xcode using one of the project templates,

immediately build it, and run it in the iOS Simulator. The application quits when you click the Home button

(or press it on a device). To launch the application, click its icon in Simulator. It may even have additional

behaviors; for example, with an application made from the Utility Application template, the initial view "flips”

to a second view when you click or tap the information (“i”) icon.

Imagine what you could do with a little code.

iOS Note: The features and behavior of an application running in iOS are considerably different from a Mac

OS X application, largely because it runs in a more constrained environment. For discussions of application

capabilities and constraints in iOS, see iOS Application Programming Guide.

In terms of programming effort, Cocoa gives you, the developer, much that is free and much that is low-cost.

Of course, to become a productive Cocoa developer means becoming familiar with possibly new concepts,

design patterns, programming interfaces, and development tools, and this effort is not negligible. But

familiarity yields greater productivity. Programming becomes largely an exercise in assembling the

programmatic components that Cocoa provides along with the custom objects and code that define your

program’s particular logic, then fitting everything together.

What follows is a short list of how Cocoa adds value to an application with only a little (and sometimes no)

effort on your part:

● Basic application framework—Cocoa provides the infrastructure for event-driven behavior and for

management of applications, windows, and (in the case of Mac OS X) workspaces. In most cases, you

won’t have to handle events directly or send any drawing commands to a rendering library.

● User-interface objects—Cocoa offers a rich collection of ready-made objects for your application’s user

interface. Most of these objects are available in the library of Interface Builder, a development application

for creating user interfaces; you simply drag an object from the library onto the surface of your interface,

configure its attributes, and connect it to other objects. (And, of course, you can always instantiate,

configure, and connect these objects programmatically.)

Here is a sampling of Cocoa user-interface objects:

Features of a Cocoa Application

CHAPTER 1

What Is Cocoa?

●

Windows

●

Text fields

●

Image views

●

Date pickers

●

Sheets and dialogs

●

Segmented controls

●

Table views

●

Progress indicators

●

Buttons

●

Sliders

●

Radio buttons (Mac OS X)

●

Color wells (Mac OS X)

●

Drawers (Mac OS X)

●

Page controls (iOS)

●

Navigation bars (iOS)

●

Switch controls (iOS)

Cocoa in Mac OS X also features technologies that support user interfaces, including those that promote

accessibility, perform validation, and facilitate the connections between objects in the user interface and

custom objects.

● Drawing and imaging—Cocoa enables efficient drawing of custom views with a framework for locking

graphical focus and marking views (or portions of views) as “dirty.” Cocoa includes programmatic tools

for drawing Bezier paths, performing affine transforms, compositing images, generating PDF content,

and (in Mac OS X) creating various representations of images.

● System interaction—In Mac OS X, Cocoa gives your application ways to interact with (and use the

services of) the file system, the workspace, and other applications. In iOS, Cocoa lets you pass URLs to

applications to have them handle the referenced resource (for example, email or websites); it also provides

support for managing user interactions with files in the local system and for scheduling local notifications.

● Performance—To enhance the performance of your application, Cocoa provides programmatic support

for concurrency, multithreading, lazy loading of resources, memory management, and run-loop

manipulation.

● Internationalization—Cocoa provides a rich architecture for internationalizing applications, making it

possible for you to support localized resources such as text, images, and even user interfaces. The Cocoa

approach is based on users’ lists of preferred languages and puts localized resources in bundles of the

application. Based on the settings it finds, Cocoa automatically selects the localized resource that best

Features of a Cocoa Application 19

CHAPTER 1

What Is Cocoa?

matches the user’s preferences. It also provides tools and programmatic interfaces for generating and

accessing localized strings. Moreover, text manipulation in Cocoa is based on Unicode by default, and

is thus an asset for internationalization.

● Text—In Mac OS X, Cocoa provides a sophisticated text system that allows you to do things with text

ranging from the simple (for example, displaying a text view with editable text) to the more complex,

such as controlling kerning and ligatures, spell checking, regular expressions, and embedding images

in text. Although Cocoa in iOS has no native text system (it uses WebKit for string drawing) and its text

capabilities are more limited, it still includes support for spellchecking, regular expressions, and interacting

with the text input system.

● Preferences—The user defaults system is based on a systemwide database in which you can store global

and application-specific preferences. The procedure for specifying application preferences is different

for Mac OS X and iOS.

● Networking—Cocoa also offers programmatic interfaces for communicating with servers using standard

Internet protocols, communicating via sockets, and taking advantage of Bonjour, which lets your

application publish and discover services on an IP network.

In Mac OS X, Cocoa includes a distributed objects architecture that allows one Cocoa process to

communicate with another process on the same computer or on a different one. In iOS, Cocoa supports

the capability for servers to push notifications to devices for applications registered to received such

notifications.

● Printing—Cocoa on both platforms supports printing. Their printing architecture lets you print images,

documents, and other application content along a range of control and sophistication. At the simplest

level, you can print the contents of any view or print an image or PDF document with just a little code.

At a more complicated level, you can define the content and format of printed content, control how a

print job is performed, and do pagination. In Mac OS X, you can add an accessory view to the Print dialog.

● Undo management—You can register user actions that occur with an undo manager, and it will take

care of undoing them (and redoing them) when users choose the appropriate menu items. The manager

maintains undo and redo operations on separate stacks.

● Multimedia—Both platforms programmatically support video and audio. In Mac OS X, Cocoa offers

support for QuickTime video.

● Data exchange—Cocoa simplifies the exchange of data within an application and between applications

using the copy-paste model. In Mac OS X, Cocoa also supports drag-and-drop models and the sharing

of application capabilities through the Services menu.

Cocoa in Mac OS X has a couple of other features:

● Document-based applications—Cocoa specifies an architecture for applications composed of a potentially

unlimited number of documents, with each contained in its own window (a word processor, for example).

Indeed, if you choose the “Document-based application” project type in Xcode, many of the components

of this sort of application are created for you.

● Scripting— Through application scriptability information and a suite of supporting Cocoa classes, you

can make your application scriptable; that is, it can respond to commands emitted by AppleScript scripts.

Applications can also execute scripts or use individual Apple events to send commands to, and receive

data from, other applications. As a result, every scriptable application can supply services to both users

and other applications.

Features of a Cocoa Application

CHAPTER 1

What Is Cocoa?

剩余199页未读，继续阅读

qys16456

粉丝: 0

Cocoa入门指南：探索苹果开发环境的关键概念与设计模式

Cocoa框架基础与Objective-C应用详解

Cocoa框架基础指南

Cocoa编程基础指南：探索Cocoa框架

CocoaFundamentals.pdf

基于遗传算法的动态优化物流配送中心选址问题研究（Matlab源码+详细注释）,遗传算法与免疫算法在物流配送中心选址问题的应用详解（源码+详细注释，Matlab编写，含动态优化与迭代，结果图展示）,遗传

SpringBoot博客项目.zip(毕设&课设&实训&大作业&竞赛&项目)

基于改进蚁群算法与动态窗口法的多机器人路径规划与避障算法研究：去除冗余点、实现全局与局部实时动态规划,基于改进蚁群算法与动态窗口法的多机器人路径规划与避障算法研究：去除冗余点，实现全局与局部实时动态规

C语言epoll的实例服务端用法

Malab Simulink MW级直驱风机模型解析及参考文献资源分享,基于Malab Simulink构建的MW级直驱风机模型及其相关参考文献,Malab Simulink MW级直驱风机模型，附赠

GVIM，WINDOWS版本的VIM

最新资源