Tumblr iOS architecture

Transcript

1. 1.

   iOS architecture Bryan Irace August 5, 2014

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   Purpose of this talk • The iOS codebase should not

   be this magical, black box that you’re scared to look at or touch • All engineers should feel comfortable reading through the code (and opening pull requests)
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   Relational DB File system Tumblr API Local storage Networking and

   storage Run loop (waits for user interaction)
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   Sync engine UI Sync engine User requested posts User created

   a post, liked/followed something, etc. New posts persisted No Internet? No problem Local storage Outgoing posts are queued, retried when connected Fetch new posts if connected, no worries if not
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   Core Data Basically an ORM, but don’t call it that

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   Our database is (mostly) just a cache Provides speed plus

   a nice offline experience without complication
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   Controller Controller View View MVC Controller View View View View

   What you see on screen and interact with Exists in a hierarchy Drawn programatically or using a visual editor (Interface Builder) Manages a screenful (or so) of information Responds to user interaction Contains only presentation logic Has a single view Populates its view with data
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   Adaptive layout • iOS 1-7 • Check if we’re running

   on an iPhone or iPad • Check if we’re in portrait or landscape • iOS 8 • At any point, app will be either vertically/horizontally “regular” or “compact” • This can change based on rotation, other factors
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   Post rendering <p><a href="http:// ryan.tumblr.com/post/ 93783287034/the-site-may- crash-16-bitch-met- david">ryan</a>:</p> <blockquote> <p>The

   site may crash. <a href="http:// tmblr.co/mqneDxY- aNcK8DhWHP23qvw">16- bitch</a> met <a href="http://tmblr.co/ mJmaPYlIVDe7tP9jhKEHlRw"> david</a>.</p> </blockquote> <p>Tumblr - making dreams come true (for David)</p> API response XML parser Mapping of character ranges to semantic section types (and attributes) Output string + data structure Or “Why inline embeds and stuff don’t show up”
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    <p> <a href=“http:// ryan.tumblr.com/post/ 93783287034/the-site-may- crash-16-bitch-met- david">ryan</a>: </p> <blockquote> <p>The

    site may crash. <a href="http://tmblr.co/ mqneDxY- aNcK8DhWHP23qvw">16-bitch</ a> met <a href=“http:// tmblr.co/ mJmaPYlIVDe7tP9jhKEHlRw">da vid</a>. </p> </blockquote> <p> Tumblr - making dreams come true (for David) </p> (0, 4): [ { type: 'link', attributes: { url: ‘http://ryan.tumblr.com/post/…’ } } ], (0, 6): [ { type: 'paragraph' } ], (46, 45): [ { type: 'paragraph' } ], (6, 40): [ { type: 'blockquote' }, { type: 'paragraph' } ], (26, 8): [ { type: 'link', attributes: { url: ‘http://tmblr.co/…’ } } ], (39, 5): [ { type: 'link', attributes: { url: ‘http://tmblr.co/…’ } } ] ryan:\nThe site may crash. 16-bitch met david.\nTumblr - making dreams come true (for David)
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    TextKit NSMutableAttributedString *string = [[NSMutableAttributedString alloc] initWithString: @"ryan:\nThe site may

    crash. 16-bitch met david.\nTumblr - making dreams come true (for David)"]; ! // Loop through ranges, add the right attributes to each range ! [postContent addAttributes:@{ NSLinkAttributeName : [NSURL URLWithString:@“http://ryan.tumblr.com/post/…”] } range:NSMakeRange(0, 4)]; ! // Lots of work required to support things like nested blockquote indentation, nested lists, inline images, etc.
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    Yes, I realize we’re kind of implementing a web browser

    here All in the name of performance
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    GIFs • Save each individual frame as a JPEG (plus

    a metadata file) • Play by looping through the individual frames • Don’t read them all into memory at once
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    • Think Gems/Bundler, NPM, etc. • Used for both internal

    and third-party dependencies • Downloads as well as integrates with Xcode project file, compilation settings, etc.
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    Internal libraries BRYMailToURIParser*
 BRYParseKeyboardNotification*
 SnoopySDK
 TMCache*
 TMTumblrSDK*
 TMVideoPlayer
 TumblrCommon *

    Open source
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    Third-party libraries CHTCollectionViewWaterfallLayout
 GRMustache
 HockeySDK
 JCKeyPathValidator
 JRSwizzle
 MTMigration
 PocketAPI
 ObjectiveCHTMLParser


    Reachability
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    Application lifecycle • Apps can be purged from memory at

    any time, if iOS needs to reclaim memory • iOS 7 added “background fetch” – app can periodically update itself even if it had previously been killed • Apps can perform “background tasks” (within reason) • e.g. User creates a post and then backgrounds the app – post will continue uploading
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    Push notifications Notification App is foregrounded App is backgrounded App

    is foregrounded and given payload App is given payload immediately iOS displays notification without app’s involvement
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    Inter-app communication • Apps define protocols that they can handle,

    e.g. “tumblr://“ • We’ve support a number of URLs, including: • tumblr://x-callback-url/tag?tag=gif • tumblr://x-callback-url/blog?blogName=bryan • tumblr://x-callback-url/quote? quote=Quote&source=Source • x-callback-url is an unofficial specification for how iOS URLs should be structured • x-success and x-error URL parameters are used to return the user to the app where they came from
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    Inter-app communication Apps can also register to open files of

    a certain type, e.g. JPEG or MP4
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    Inter-app communication iOS 8 allows apps to expose “share extensions”