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Swift Essentials
Swift Essentials

Swift Essentials: Get up and running lightning fast with this practical guide to building applications with Swift

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Profile Icon Bandlem Limited Profile Icon Alex Blewitt
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R$306.99
Full star icon Full star icon Full star icon Full star icon Half star icon 4.8 (4 Ratings)
Paperback Dec 2014 228 pages 1st Edition
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R$49.99 R$245.99
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Arrow left icon
Profile Icon Bandlem Limited Profile Icon Alex Blewitt
Arrow right icon
R$306.99
Full star icon Full star icon Full star icon Full star icon Half star icon 4.8 (4 Ratings)
Paperback Dec 2014 228 pages 1st Edition
eBook
R$49.99 R$245.99
Paperback
R$306.99
Subscription
Free Trial
Renews at R$50p/m
eBook
R$49.99 R$245.99
Paperback
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Swift Essentials

Chapter 2. Playing with Swift

Xcode ships with both a command line interpreter (covered in Chapter 1, Exploring Swift) and a graphical interface called playground that can be used to prototype and test Swift code snippets. Code typed into the playground is compiled and executed interactively, which permits a fluid style of development. In addition, the user interface can present a graphical view of variables as well as a timeline, which can show how loops are executed. Finally, playgrounds can mix and match code and documentation, leading to the possibility of providing example code as playgrounds and using playgrounds to learn how to use existing APIs and frameworks.

This chapter will present the following topics:

  • How to create a playground
  • Displaying values in the timeline
  • Presenting objects with Quick Look
  • Running asynchronous code
  • Using playground live documentation
  • Generating playgrounds with Markdown and AsciiDoc
  • Limitations of playgrounds

Getting started with playgrounds

When Xcode is started, a welcome screen is shown with various options, including the ability to create a playground. Playgrounds can also be created from the File | New | Playground menu.

Getting started with playgrounds

Creating a playground

Using either the Xcode welcome screen (which can be opened by navigating to Window | Welcome to Xcode) or navigating to File | New | Playground, create MyPlayground in a suitable location targeting iOS. Creating the playground on the Desktop will allow easy access to test Swift code, but it can be located anywhere on the filesystem.

Playgrounds can be targeted either towards OS X applications or towards iOS applications. This can be configured when the playground is created, or by switching to the Utilities view by navigating to View | Utilities | Show File Inspector or pressing Command + Option + 1 and changing the dropdown from OS X to iOS or vice versa.

Creating a playground

When initially created, the playground will have a code snippet that looks as follows:

// Playground...

Displaying objects with QuickLook

The playground timeline can display objects as well as numbers and simple strings. It is possible to load and view images in a playground using classes such as UIImage (or NSImage on OS X). These are known as QuickLook supported objects, and by default include:

  • Strings (attributed and unattributed)
  • Views
  • Class and struct types (members are shown)
  • Colors

Tip

It is possible to build support for custom types in Swift, by implementing a debugQuickLookObject method that returns a graphical view of the data.

Showing colored labels

To show a colored label, a color needs to be obtained first. When building against iOS, this will be UIColor; but when building against OS X, it will be NSColor. The methods and types are largely equivalent between the two, but this chapter will focus on the iOS types.

A color can be acquired with an initializer or by using one of the predefined colors that are exposed in Swift using methods:

import UIKit // AppKit for OS X
let blue = UIColor...

Advanced techniques

The playground has its own framework, XCPlayground, which can be used to perform certain tasks. For example, individual values can be captured during loops for later analysis. It also permits asynchronous code to continue to execute once the playground has finished running.

Capturing values explicitly

It is possible to explicitly add values to the timeline by importing the XCPlayground framework and calling XCPCaptureValue with a value that should be displayed in the timeline. This takes an identifier, which is used both as the title and for group-related data values in the same series. When the value history button is selected, it essentially inserts a call to XCPCaptureValue with the value of the expression as the identifier.

For example, to add the logo to the timeline automatically:

import XCPlayground
XCPCaptureValue("logo",logo)
Capturing values explicitly

It is possible to use an identifier to group the data that is being shown in a loop with the identifier representing categories of...

Playgrounds and documentation

Playgrounds can contain a mix of code and documentation. This allows a set of code samples and explanations to be mixed in with the playground itself. Although there is no way of using Xcode to add sections in the UI at present, the playground itself is an XML file that can be edited using an external text editor such as TextEdit.app.

Learning with playgrounds

As playgrounds can contain a mixture of code and documentation, it makes them an ideal format for viewing annotated code snippets. In fact, Apple's Swift Tour book can be opened as a playground file.

Xcode documentation can be searched by navigating to the Help | Documentation and API Reference menu, or by pressing Command + Shift + 0. In the search field that is presented, type Swift Tour and then select the first result. The Swift Tour book should be presented in Xcode's help system:

Learning with playgrounds

A link to download and open the documentation as a playground is given in the first section; if this is downloaded...

Limitations of playgrounds

Although playgrounds can be very powerful for interacting with code, there are some limitations that are worth being aware of. There is no debugging support in the playground. It is not possible to add a breakpoint and use the debugger and find out what the values are. Given that the UI allows tracking values—and that it's very easy to add new lines with just the value to be tracked—this is not much of a hardship. Other limitations of playgrounds include:

  • Only the simulator can be used for the execution of iOS-based playgrounds. This prevents the use of hardware-specific features that might only be present on a device.
  • The performance of playground scripts is mainly driven based on how many lines are executed and how much output is saved by the debugger. It should not be used to test the performance of performance-sensitive code.
  • Although the playground is well suited to present user interface components, it cannot be used for user input.
  • Anything...

Summary

This chapter presented playgrounds, an innovative way of running Swift code with graphical representations of values and introspection of running code. Both expressions and the timeline were presented as a way of showing the state of the program at any time, as well as graphically inspecting objects using QuickLook. The XCPlayground framework can also be used to record specific values and allow asynchronous code to be executed.

Being able to mix code and documentation into the same playground is also a great way of showing what functions exist, and how to create self-documenting playgrounds was presented. In addition, tools for the creation of such playgrounds using either AsciiDoc or Markdown (CommonMark) were introduced.

The next chapter will look at how to create an iOS application with Swift.

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Description

Whether you are a seasoned Objective-C developer or new to the Xcode platform, Swift Essentials will provide you with all you need to know to get started with the language. Prior experience with iOS development is not necessary, but will be helpful to get the most out of the book.

What you will learn

  • Explore the nuts and bolts of the Swift syntax
  • Test Swift code interactively with the REPL
  • Display graphics with QuickLook in the Swift playground
  • Present data in masterdetail applications
  • Use the Swift storyboard to manage multiscreen applications
  • Create graphical UIViews with Swift
  • Parse JSON and XML data from network sources
  • Build a standalone iOS application from start to finish
Estimated delivery fee Deliver to Brazil

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Publication date, Length, Edition, Language, ISBN-13
Publication date : Dec 26, 2014
Length: 228 pages
Edition : 1st
Language : English
ISBN-13 : 9781784396701
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Product Details

Publication date : Dec 26, 2014
Length: 228 pages
Edition : 1st
Language : English
ISBN-13 : 9781784396701
Vendor :
Apple
Category :
Languages :

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Table of Contents

9 Chapters
1. Exploring Swift Chevron down icon Chevron up icon
2. Playing with Swift Chevron down icon Chevron up icon
3. Creating an iOS Swift App Chevron down icon Chevron up icon
4. Storyboard Applications with Swift and iOS Chevron down icon Chevron up icon
5. Creating Custom Views in Swift Chevron down icon Chevron up icon
6. Parsing Networked Data Chevron down icon Chevron up icon
7. Building a Repository Browser Chevron down icon Chevron up icon
A. Appendix Chevron down icon Chevron up icon
Index Chevron down icon Chevron up icon

Customer reviews

Rating distribution
Full star icon Full star icon Full star icon Full star icon Half star icon 4.8
(4 Ratings)
5 star 75%
4 star 25%
3 star 0%
2 star 0%
1 star 0%
Charles Nichols Mar 22, 2015
Full star icon Full star icon Full star icon Full star icon Full star icon 5
Great book! I've been programming in multiple languages and platforms for years so I mostly skimmed this book for little missing bits and pieces to get me up to speed; the book walks you through the details very well. If you're doing hardcore app development in XCode and know the environment very well, which I don't, it may not be the book for you, but I'd still recommend it as a good walk through paired with Apple's Swift documentation if you have any Swift application development questions; although, you'll likely find what you need online as more people start using it. If you are an occasional Apple developer or new and want to get up to speed in XCode doing application development using Swift this book is a great place to start.
Amazon Verified review Amazon
Matteo Jan 24, 2015
Full star icon Full star icon Full star icon Full star icon Full star icon 5
This book provides you a learning path from zero to an intermediate complexity iOS app to get the ropes of the language up to a decent level. Every step is explained in extensive detail so that you never feel lost within the code. If you never coded on OSX you won't feel lost as the first chapters provide every little bit you need to start code using xCode playgrounds up to proper iOS/OSX coding. The sole requirement is obviously a recent Mac to do the code demos along with a up-to-date xCode installation.
Amazon Verified review Amazon
Damir Arh Feb 14, 2015
Full star icon Full star icon Full star icon Full star icon Full star icon 5
The author kept the initial introduction to the basic language syntax really brief and quickly made it more interesting and rewarding by replacing the command line REPL environment with Xcode integrated development environment and its playgrounds - a feature which provides a highly interactive environment for experimenting with the language. Not only that: he moved on to development of basic iOS applications, even before he covered all of the language features; introducing many of them only when they were first encountered in sample code.Major part of the book is actually a step by step guide to iOS development in Swift for complete beginners. By the end of it the readers should have enough knowledge to write their first simple iOS application even without any previous experience. Along the way all the key concepts of the API are explained in detail, as well as a couple of peculiarities originating from the Objective-C era which could cause memory leaks or prematurely released memory, if not handled correctly. Even unit testing of Swift code was mentioned and encouraged.The only thing I missed, was a more in-depth discussion of the language features and how they will impact the way the code will be written in it. Though, considering the target audience, it's not really fair to hold that against it. If nothing else, it makes up for it with a very extensive list of resources about Swift and iOS development which should satisfy even the most curious reader.
Amazon Verified review Amazon
Raúl Feb 26, 2015
Full star icon Full star icon Full star icon Full star icon Empty star icon 4
I enjoyed reading this book as it gave me some interesting tips of how to approach swift from another perspective, the command line script/compiled side of the language, which could lead to interesting backend tools that increase developers productivity.Another interesting section I was pleased to read lied within the realm of the playground, a scripting terminal with steroids I would like to call, of which the books explains methodically without going into much detail of the magic behind.With this book, you will learn to do custom views, networking, xml/json parsing, story boards, but the part I considered more important was its whole app as a GIT repository viewer, of course everything handled using swift as core language.However, I consider a big downside that the book does not include any chapters regarding unit test, or advanced swift topics (aka Functional or reactive); being said that, I would recommend it for developers of any platform, for those that have read the Apple swift books.
Amazon Verified review Amazon
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