Writing a native Mac GUI application in HaskellWriting a native Mac GUI application in Haskell...
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Transcript of Writing a native Mac GUI application in HaskellWriting a native Mac GUI application in Haskell...
Agenda• JSON Class Generator
• Joining the worlds
• Architecture
• In practice
• Retrospective
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JSON Class Generator
• Mac Application
• ~15.000 lines of Haskell
• ~ 3.000* lines of Objective-C
• Mac App Store
• Web ⬇
• Sandboxed
• lifted.software
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Demo
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Recap
• Define Classes/Enums/Methods
• Export Objective-C code
• Use code to serialize/deserialize JSON
• Drop in (HTTP-)Client to connect to Service
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How Did I Write It?
• Hardcoded types in Haskell source (2014)
• Command Line Tool (2015)
• Mac/Cocoa NSDocument based GUI App (2016)
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Evolution
• Hardcoded types in HS source (2014)
• Command Line Tool (2015)
• Mac/Cocoa NSDocument based GUI App (2016)
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> api --lang objc --def api.json --out ./src/api
Cutting Edge
• Hardcoded types in HS source (2014)
• Command Line Tool (2015)
• Mac/Cocoa NSDocument based GUI App (2016)
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Joining the Worlds
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How to Build the UI• Non-native UI
• Web
• Cross platform UI Libraries (GTK, QT)
• Native UI
• Cocoa/ObjC UI + ObjC model -> call CLT
• Cocoa/ObjC UI + HS model (together in one app)
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Adding Some Glue• Communicate to HS via FFI
• c2hs
• Bindings (HoC, ObjectiveHaskell)
• language-c-inline
• Others (Apache Thrift)
• Client-Server (no network)12
How Do We Connect ObjC to a Server that
Speaks JSON?
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JSON Code Generator!
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~3000 LoC + ~13000 LoC
~16000 LoC
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ObjC Generated
⌨ ⚙
How to Compile• Compiled languages
• Xcode, not Terminal
• Build phases
• HS to static library "-staticlib" => liba.a (ext. build tool)
• Generate API from specification file
• Compile ObjC (+Storyboards), copy asses/frameworks
• Link with liba.a libiconv
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Compile Attempts
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Application Launch
• Two runtimes to start
• Bound threads
• FFI
• -threaded
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Architecture
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Server (Haskell)
Client
Service
ApiDocument : NSDocument
WindowController
Document
RAC
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Server (Haskell)
Client
Service
ApiDocument : NSDocument
WindowController
Document
RAC
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Server (Haskell)
Client
Service
ApiDocument : NSDocument
WindowController
Document
RAC
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Client-Server (HS)• Stores model (synchronized access)
• Serves JSON API
• No HTTP needed (server hardwired)
• Blocking calls
• No latency
• One instance per Document23
Haskell Server
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Model• Undo Manager
• Outline View
• Encoding Callbacks
• Continuation Passing Style
• Performance (outline view, json serialization)
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Server (Haskell)
Client
Service
ApiDocument : NSDocument
WindowController
Document
RAC
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(ObjC) Client-Server• Powers service
• Serializes requests (Object -> JSONValue -> char *)
• Memory management
• Deserializes responses (NSData * -> JSONValue -> Object)
• Logs errors and exceptions
• Updates ModelRevisionCounter
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(ObjC) Client-Server• Powers service
• Serializes requests (Object -> JSONValue -> char *)
• Memory management
• Deserializes responses (NSData * -> JSONValue -> Object)
• Logs errors and exceptions
• Updates ModelRevisionCounter
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Memory Management• ObjC ARC
• HS GC
• Avoidance
• Request: FFI bracket
• Response: NSData allocation, ARC
• Problem: wasting memory (make model strict)29
Exception Handling
• Error reporting
• What happens if ObjC crashes?
• What happens if HS crashes?
• Problem: Lost exceptions
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Server (Haskell)
Client
Service
ApiDocument : NSDocument
WindowController
Document
RAC
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Service
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Server (Haskell)
Client
Service
ApiDocument : NSDocument
WindowController
Document
RAC
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NSDocument RAC Write
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NSDocument RAC Read
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Server (Haskell)
Client
Service
ApiDocument : NSDocument
WindowController
Document
RAC
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User Interface
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Server (Haskell)
Client
Service
ApiDocument : NSDocument
WindowController
Document
RAC
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Unidirectional Data Flow
In Practice
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Development Tools• Xcode, -debugger, for ObjC
• Haskell for Mac (Haskell.app IDE) for HS
• Sublime: for shell scrips (Haskell Shelly)
• Instruments
• Threadscope (performance), RTS opts MEM
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Debugging
41ObjC HS
Testing
• Unit tests for ObjC and HS
• UI tests
• Server interface tests
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Retrospective
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Challenges
• Getting started
• Building, Setup, Architecture
• Debugging
• Persistence. All problems solvable.
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Reflecting• Haskell Language
• Two Languages in one app
• Domain specific
• Cross platform
• Swift
• Cross platform UI Libraries45
Where to get started• Tim Scheffler's blog (1) (2) (3)
• FFI section of HS2010 report
• Dropbox CppCon2014 Cross Platform (1) (2)
• Libs: language-c-inline (talk) (github) (hackage)
• Haskell for Mac IDE
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Questions?
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