iOS Apps with REST APIs: Building Web-Driven Apps in Swift

241 Pages·2015·9 MB·English

by  Christina Moulton

iOS Apps with REST APIs
Building Web-Driven Apps in Swift
Christina Moulton
©2015 Teak Mobile Inc. All rights reserved. Except for the use in any review, the reproduction or
utilization of this work in whole or in part in any form by any electronic, mechanical or other
means is forbidden without the express permission of the author.
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Contents
Thanks i
1. FromJSONAPItoSwiftApp 1
1.1 WhatWillYouBeAbletoDo? 1
1.2 WhoIsThisBookFor? 2
1.3 WhoIsThisBookNotFor? 2
1.4 UsingThisBook 2
1.5 WhatWeMeanByWebServices/APIs/REST/CRUD 3
1.6 JSON 3
1.7 Versions 3
1.8 SourceCode 4
1.9 Disclaimer 4
1.10 Trademarks 4
2. OurApp’sRequirements 6
2.1 MatchTaskstoEndpoints 7
2.2 UserInterface 9
2.3 APIRequirements 10
2.4 MakeaPlan 11
3. SwiftJSONParsing&NetworkingCalls101 13
3.1 SimpleRESTAPICallswithSwift 13
3.2 RESTAPICallswithAlamofire&SwiftyJSON 22
3.3 AlamofireRouter 27
3.4 StronglyTypedGETandPOSTCallswithAlamofire 33
3.5 AndThat’sAll 42
4. WhyIUseLibrariesLikeAlamofire 43
5. HookingUpaRESTAPItoaTableView 44
5.1 OurSwiftProject 44
5.2 AnalyzingtheAPIJSONResponse 47
5.3 SettingUptheTableView 52
5.4 Getting&ProcessingtheAPIResponse 60
5.5 AndThat’sAll 66
CONTENTS
6. CustomHeaders 68
6.1 SessionHeaders 68
6.2 PerRequestHeaders 69
6.3 HeadersinURLRequestConvertible 69
6.4 AndThat’sAllForHeaders 70
7. LoadingUITableViewCellImagesfromanAPI 71
7.1 LoadingUIImagesfromURLs 72
7.2 UITableViewCellImagesfromURLs 72
7.3 Enhancements 75
7.4 CachingImages 76
7.5 ABetterCache:PINRemoteImage 80
7.6 AndThat’sAll 81
8. Pagination,a.k.a.,LoadMoreonScroll 82
8.1 WhereistheNextPage? 82
8.2 FetchingandAppending 85
8.3 IntegratingwiththeViewController 87
8.4 WhentoLoadMoreGists? 89
8.5 AndThat’sAllforPagination 91
9. PulltoRefresh 92
9.1 AddingPulltoRefresh 92
9.2 ShowingtheLastRefreshedTime 94
9.3 AndThat’sAll 96
10. Authentication 97
10.1 TheDocs 97
10.2 BasicAuth:Username/Password 97
10.3 HTTPHeaderAuthentication 102
10.4 AlamofireValidation 104
10.5 OAuth2.0 106
10.6 DisplayingtheResults 137
10.7 UnauthorizedResponses:404vs401 149
10.8 AndThat’sAll 151
11. SwitchingLists 152
11.1 SettingUptheUI 152
11.2 SharingaCompletionHandler 156
11.3 AndThat’sAll 160
12. SwitchingBetweenViewControllersandMoreJSONParsing 161
12.1 JSONParsing:Arrays&Dates 161
12.2 ParsingDatesinJSON 164
CONTENTS
12.3 ConfiguringtheDetailViewController 166
12.4 PassingDatainaSegue 171
12.5 AddingaTableView 172
12.6 DisplayingGistFileContent 178
12.7 AndThat’sAll 179
13. AddingMoreAPICalls-Starring 180
13.1 IstheGistStarred? 180
13.2 StarredStatusintheTableView 181
13.3 PUTandDELETECallstoStarandUnstarGists 184
13.4 AuthorizationCheck 186
13.5 AndThat’sAll 190
14. DeletingGists 191
14.1 DELETEAPICall 191
14.2 UserInterface:TableViewDeleteFeatures 192
14.3 AndThat’sAll 195
15. CreatingGistsandClearingtheCache 196
15.1 POSTAPICallwithNestedJSONParameters 196
15.2 CreatinganInputFormwithValidation 200
15.3 AndThat’sAll 208
16. WhatifThey’reOffline? 209
16.1 HowDoWeKnow? 209
16.2 SaveaLocalCopy 221
16.3 Databases 227
17. WhatNext? 229
17.1 UserInterface 229
17.2 TesttheUserExperience 229
17.3 SuggestedExercises 229
17.4 DidIMissAnything? 230
ABriefIntroductiontoCocoaPods 231
AddingaCocoaPodtoaProject 231
WhatDoesthePodfileMean? 232
OtherOptions 233
Dependencies 233
CocoaPodsVersionNumbers 233
UpdatingCocoaPods 234
Thanks
Without a few key people this book wouldn’t have happened. Most of all, thanks to Jeff Moulton
forputtingupwithmyexcessivefocusoncoding&writing,evenwhilelivingona34’sailboat.Jeff
alsotookthecoverphoto.
Thanksalsoto:
• MyTwitterpeepsforsupport&fav’s
• @BugKrusha¹&theiOSDevelopers²community
• GitHub
• LeanPub
• Everyone who gave feedback or asked questions about the book or GrokSwift.com³. Every
littlebithelpsmakethebookbetterforyou.
¹http://twitter.com/BugKrusha
²http://ios-developers.io
³https://grokswift.com
i
1. From JSON API to Swift App
YouneedtobuildaniOSapparoundyourteam’sAPIorintegrateathirdpartyAPI.Youneedaquick,
clearguidetodemystifyXcodeandSwift.NoesotericdetailsaboutCoreAnythingormathematical
analysisof flatMap.Onlythenittygrittythatyouneedtogetrealworkdonenow:pullingdatafrom
yourwebservicesintoaniOSapp,withouttossingyourMacBookorMacMinithroughawindow.
You just need the bare facts on how to get CRUD done on iOS. That’s what this book will do for
you.
1.1 What Will You Be Able to Do?
Afterreadingthisbookyou’llbeableto:
• AnalyzeaJSONresponsefromawebservicecallandwriteSwiftcodetoparseitintomodel
objects
• Displaythosemodelobjectsinatableviewsothatwhentheuserlaunchestheapptheyhave
anicelisttoscrollthrough
• AddauthenticationtousewebservicecallsthatrequireOAuth2.0,ausername/password,or
atoken
• Transitionfromthemaintableviewtoadetailviewforeachobject,possiblymakinganother
webservicecalltogetmoreinfoabouttheobject
• Letusersadd,modifyanddeleteobjects(aslongasyourwebservicesupportsit)
• Hookintomorewebservicecallstoextendyouapp,likeaddinguserprofilesorlettingusers
submitcommentsorattachphotostoobjects
Toachievethosegoalswe’llbuildoutanappbasedontheGitHubAPI,focusingongists.(Ifyou’re
not familiar with gists, they’re basically just text snippets, often code written a GitHub user.) Your
model objects might be bus routes, customers, chat messages, or whatever kind of object is core to
yourapp.We’llstartbyfiguringouthowtomakeAPIcallsinSwiftthenwe’llstartbuildingoutour
apponefeatureatatime:
• Showalistofallpublicgistsinatableview
• Loadmoreresultswhentheuserscrollsdown
• Letthempulltorefreshtogetthelatestpublicgists
• LoadimagesfromURLsintotableviewcells
• UseOAuth2.0forauthenticationtogetlistsofprivateandstarredgists
1
FromJSONAPItoSwiftApp 2
• Haveadetailviewforeachgistshowingthetext
• Allowuserstoaddnewgists,starandunstargists,anddeletegists
• Handle not having an internet connection with warnings to the user and saving the gists on
thedevice
1.2 Who Is This Book For?
• SoftwaredevelopersgettingstartedwithiOSbutexperiencedinotherlanguages
• Front-enddevslookingtoimplementnativeUIsforiOSapps(noCSS,ohnoes!)
• Back-enddevstaskedwithgettingthedataintotheuser’shandsoniOS
• Android, Windows Phone, Blackberry, Tizen, Symbian & Palm OS devs looking to expand
theirwebservicebackedappstoiOS
• AnyonewhosebossisstandingovertheirshoulderaskingwhytheAPIdataisn’tshowingup
inthetableviewyet
1.3 Who Is This Book Not For?
• Completenewcomerstoprogramming,youshouldhaveadecentgraspofatleastoneobject-
orientedprogramminglanguageorhavecompletedseveralintrotoiOStutorials
• Designers, managers, UX pros, … It’s a programming book. All the monospace font inserts
willprobablydriveyoucrazy.
• Cross-platform developers dedicated to their tools (including HTML5 & Xamarin), this is all
Swift&nativeUI,allthetime
• Programmersbuildingappsthathavelittleornowebserviceinteraction
• Gamedevs,unlessyou’retyinginaREST-likeAPI
1.4 Using This Book
Thisbookismostlywrittenasatutorialinimplementingthegistsapp.Dependingonhowyoulearn
bestandhowurgentlyyouneedtoimplementyourownapp,therearetwodifferentapproachesyou
mighttake:
1. Work through the tutorials as written, creating an app for GitHub Gists. You’ll understand
howthatappworksandlaterbeabletoapplyittoyourownapps.
2. Read through the tutorials but implement them for your own app and API. Throughout the
text I’ll point out where you’ll need to analyze your own requirements and API to help you
figure out how to modify the example code to work with your API. Those tips will look like
this:
FromJSONAPItoSwiftApp 3
Listthetasksoruserstoriesforyourapp.Comparethemtothelistforthegistsapp,focusing
onthenumberofdifferentobjects(likestars,users,andgists)andthetypesofactiontaken
(likeviewingalist,viewinganobject’sdetails,adding,deleting,etc.).
We’llstartwiththattaskinthenextchapter.We’llanalyzeourrequirementsandfigureoutjustwhat
we’re going to build. Then we’ll start building the gists app, right after an introduction to making
networkcallsandparsingJSONinSwift.
1.5 What We Mean By Web Services / APIs / REST /
CRUD
Like anything in tech there are plenty of buzzwords around web services. For a while it was really
trendy to say your web services were RESTful. If you want to read the theory behind it, head over
toWikipedia¹.For our purposesin this book,all wemeanby“REST webservice”orevenwhen we
say “web service” or “API” is that we can send an HTTP request and we get back some data in a
formatthat’seasytouseinourapp.UsuallytheresponsewillbeinJSON.
Webservicesarewonderfulsincetheyletyouuseexistingsystemsinyourownapps.There’salways
a bit of a learning curve with any web service that you’re using for the first time since every one
hasitsownquirks.Mostoftheintegrationissimilarenoughthatwecangeneralizehowtointegrate
themintoouriOSapps.
If you want an argument about whether or not a web service is really RESTful you’re not going to
findithere.We’vegotworkthatjustneedstogetdone.
1.6 JSON
Inthisbookwe’regoingtodealwithwebservicesthatreturnJSON.JSONishugelycommonthese
days so it’s probably what you’ll be dealing with. Of course, there are other return types out there,
like XML. This book won’t cover responses in anything but JSON but it will encapsulate the JSON
parsingsothatyoucanreplaceitwithwhateveryouneedtowithouthavingtotouchatonofcode.
IfyouaredealingwithXMLresponseyoushouldlookatNSXMLParser².
1.7 Versions
Thisisversion1.1.1ofthisbook.ItusesSwift2.0,iOS9,andXcode7.1.Whenweuselibrarieswe’ll
explicitly list the versions used. The most commonly used ones are Alamofire 3.1 and SwiftyJSON
2.3.
¹https://en.wikipedia.org/wiki/Representational_state_transfer
²https://developer.apple.com/library/mac/documentation/Cocoa/Reference/Foundation/Classes/NSXMLParser_Class/