Difference between revisions of "User:JRV"
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| − | I'm developing a tutorial on this page (slowly). I'm keeping it here so I can check out |
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| − | format, figures, etc. before putting the whole think in the Tutorial area. |
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| − | |||
| − | -------------------------------------------------------------- |
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| − | Here, we develop a simple (Mac) Xcode project using Cocoa, the Interface |
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| − | Builder (IB). The project follows the Model-View-Control design pattern |
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| − | encouraged by Apple, with the View and Control entirely in Cocoa and IB, and |
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| − | the Model in Haskell. |
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| − | |||
| − | This is far from fulfilling the request found in the |
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| − | [[Missing_tutorials | Missing tutorials]] page. |
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| − | But it is a simple process, not requiring |
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| − | adding any Xcode plugins, or other extra applications. |
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| − | |||
| − | It assumes you know something about Xcode, and something about Haskell. |
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| − | Its not an objective-c bridge. |
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| − | |||
| − | == Why? == |
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| − | Why would you want to do this? Those with Xcode/Cocoa experience will not |
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| − | need an explanation. On the chance that someone else is browsing here, |
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| − | I'll list a few things. |
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| − | |||
| − | * Cocoa is not a language, it is a vast library of Objective-C objects. |
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| − | |||
| − | * Cocoa covers tasks such as: |
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| − | ** windowing, |
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| − | ** displaying tables, outlines, trees, |
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| − | ** text fields (with built in editing), |
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| − | ** pretty easy printing, with pdf automatically available, and |
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| − | ** on and on... |
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| − | |||
| − | * Objective-C is built on C, and is basically syntactic sugar for C. |
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| − | |||
| − | Together with Interface Builder, one can define most user interfaces with |
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| − | simple drag and drop from a library of element, then connect them with your |
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| − | code by dragging and drop in the IB screen. |
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| − | |||
| − | You automatically get full integration with the Mac system. You get the |
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| − | Mac Aqua look. |
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| − | |||
| − | Enough said. What Cocoa doesn't provide are the tools for mathematical |
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| − | modeling of an application domain that Haskell provides. Parsing comes |
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| − | immediately to mind. |
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| − | |||
| − | In the interest of full disclosure—I'm not an old time Mac person. I've |
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| − | had my Mac for two years. I only decided to learn Objective-C and Cocoa |
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| − | after I explored doing an application using Python and Qt, and someone in |
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| − | the Python community said “Objective-C is easy. Why don't you write a real |
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| − | Mac application”. Neither am I a Haskell expert. Although I've tinkered |
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| − | with Haskell for a long time (and it is probably my favorite language), |
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| − | I've just come back to it after a couple years away. |
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| − | |||
| − | == Overview == |
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| − | [[image:JRV_CocoaHaFib_before.png|thumb|350px|right]] |
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| − | Here are screen shost of the simple application we will develop. The first |
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| − | shows the application widow (together with the menu automatically generated |
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| − | by Xcode), ready to enter a number. |
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| − | |||
| − | The second shows the same scene after entering a number in the text box, |
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| − | and pressing “return”. |
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| − | |||
| − | The entire user interface was built in a short time using the graphical |
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| − | Interface Builder, by dragging text the entry box, and the labels from a |
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| − | library of “controls” onto the window. Notice that the labels are dynamic, |
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| − | in the line “Fibonacci Number for n = … is: … ”. |
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| − | |||
| − | I won't discuss Interface Builder any further in this tutorial. |
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| − | |||
| − | [[image:JRV_CocoaHaFib_after.png|thumb|350px|right]] |
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| − | |||
| − | == The Haskell module == |
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| − | For this test I used the same code as used in |
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| − | [[Calling_Haskell_from_C|Calling Haskell from C], with some slight |
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| − | modifications. Here is the Haskell code, in a file called ''FibTest.hs''. |
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| − | |||
| − | <haskell> |
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| − | |||
| − | {-# LANGUAGE ForeignFunctionInterface #-} |
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| − | |||
| − | module FibTest where |
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| − | |||
| − | import Foreign.C.Types |
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| − | |||
| − | fibonacci :: Int -> Int |
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| − | fibonacci n = fibs !! n |
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| − | where fibs = 0 : 1 : zipWith (+) fibs (tail fibs) |
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| − | |||
| − | fibonacci_hs :: CInt -> CInt |
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| − | fibonacci_hs = fromIntegral . fibonacci . fromIntegral |
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| − | |||
| − | foreign export ccall fibonacci_hs :: CInt -> CInt |
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| − | |||
| − | </haskell> |
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| − | |||
| − | We compile this with ghc, viz: |
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| − | |||
| − | $ ghc -c -O FibTest.hs |
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| − | |||
| − | This produces the following files that we will import into Xcode: |
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| − | |||
| − | * ''FibTest.o'' |
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| − | * ''FibTest_stub.h'' |
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| − | * ''FibTest_stub.o'' |
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| − | |||
| − | and the following files that we won't need: |
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| − | |||
| − | * ''FibTest_stub.c'' |
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| − | * ''FibTest.hi'' |
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| − | |||
| − | == Import into Xcode project == |
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| − | First we start an Xcode project in the usual way. I started this as a |
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| − | plain Cocoa application. I called my application CocoaHaskellFib. |
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| − | |||
| − | Several steps can be done in any order: |
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| − | |||
| − | === Copy Files === |
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| − | FibTest.o, FibTest_stub.h, and FibTest_stub.o into the folder where |
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| − | you have saved your CocoaHaskellFib project. |
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| − | |||
| − | Then add them to the project by Project ➝ Add To Project . |
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| − | |||
| − | === Create application class === |
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| − | Next, create a Cocoa Objective-C class using the Xcode menu, File→New. |
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| − | I named mine CocoaFib. Xcode will create both an interface file (.h) and an |
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| − | implementation file (.m). |
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| − | |||
| − | Here is my interface file: |
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| − | |||
| − | <pre> |
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| − | #import <Cocoa/Cocoa.h> |
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| − | |||
| − | |||
| − | @interface CocoaFib : NSObject { |
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| − | IBOutlet NSTextField *integerInput; |
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| − | IBOutlet NSTextField *fibOutput; |
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| − | IBOutlet NSTextField *forNis; |
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| − | |||
| − | } |
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| − | |||
| − | -(IBAction)generate:(id)sender; |
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| − | |||
| − | |||
| − | @end |
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| − | </pre> |
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| − | |||
| − | The three outlets are for the user input, fibonacci number output, and the |
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| − | label. |
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| − | |||
| − | And here is my implementation code: |
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| − | |||
| − | <pre> |
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| − | #import "CocoaFib.h" |
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| − | #include "HsFFI.h" |
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| − | #include "FibTest_stub.h" |
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| − | |||
| − | @implementation CocoaFib |
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| − | -(IBAction)generate:(id)sender{ |
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| − | int i = [integerInput intValue]; |
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| − | NSLog(@" in generate, integer input is %d\n",i ); |
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| − | unsigned int j = fibonacci_hs(i); |
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| − | [forNis setIntValue:i]; |
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| − | [fibOutput setIntValue:j]; |
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| − | |||
| − | } |
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| − | |||
| − | |||
| − | -(void)dealloc{ |
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| − | hs_exit(); |
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| − | [super dealloc]; |
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| − | } |
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| − | |||
| − | |||
| − | @end |
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| − | |||
| − | </pre> |
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| − | |||
| − | Note the include lines for 1) ''hsFFI.h'', and ''FibTest_stub.h''. |
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| − | |||
| − | Note also the ''hs_exit'' call in ''dealloc''. |
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| − | |||
| − | === Modify main.m === |
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| − | When creating a Cocoa project, Xcode automatically generates a file |
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| − | ''main.m''. Normally, one never touches this file. However, when using |
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| − | a Haskell module, one needs to initialize the Haskell run-time by calling |
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| − | ''hs_init''. Normally, I would do this in an ''init'' call of |
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| − | ''CocoaFib.m'', rather than in ''main.m'', but since ''hs_init'' needs an |
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| − | ''argc'' and ''argv'', and since ''main.m'' already has them hanging |
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| − | around, I took the easy way out. |
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| − | |||
| − | Here is ''main.m'' |
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| − | |||
| − | <pre> |
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| − | #import <Cocoa/Cocoa.h> |
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| − | #include "FibTest_stub.h" |
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| − | int main(int argc, char *argv[]) |
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| − | { |
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| − | hs_init(&argc, &argv); |
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| − | return NSApplicationMain(argc, (const char **) argv); |
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| − | } |
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| − | |||
| − | |||
| − | </pre> |
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| − | The only changes to the main.m provided by Xcode are the addition of |
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| − | ''include "FibTest_stub.h"'' and the call to ''hs_init''. |
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| − | |||
| − | == Compile and run == |
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| − | This is the easy part. Just kidding. It should be easy, if it were easy |
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| − | to make a library or executable containing ''FibTest.o'', |
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| − | ''FibTest_stub.o'' and all their dependencies. Unfortunately I've been |
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| − | unable to do that, in spite of spending most of my spare time for a week |
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| − | trying, and posting questions on ''Haskell-cafe''. |
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| − | Anyway, here is how I did it. If you have a better way, here is a good |
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| − | place to edit this tutorial! |
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| − | |||
| − | === Build and go, the first time === |
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| − | === Iterate build and go === |
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| − | === Symlink renamed libgmp.a === |
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| − | == To do == |
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