Adopting MVC in Cocoa
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A presentation I delivered to ACCU in 2009 about using MVC (model-view-controller) in Cocoa to make best use of the frameworks and maximise code reuse.
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Adopting MVC in Cocoa
- 1. Adopting Model-View- Controller in Cocoa and Objective-C Graham Lee http://twitter.com/iamleeg
- 2. Memory Lane
- 3. Memory Lane • 1980s: Brad Cox at StepStone adds Smalltalk messaging to C. Some guy named Bjarne invents “C with Classes”.
- 4. Memory Lane • 1980s: Brad Cox at StepStone adds Smalltalk messaging to C. Some guy named Bjarne invents “C with Classes”. • 1986: Cox authors Object Oriented Programming: an evolutionary approach, ObjC is born
- 5. Memory Lane • 1980s: Brad Cox at StepStone adds Smalltalk messaging to C. Some guy named Bjarne invents “C with Classes”. • 1986: Cox authors Object Oriented Programming: an evolutionary approach, ObjC is born • 1988: NeXT licence ObjC from StepStone
- 6. Memory Lane • 1980s: Brad Cox at StepStone adds Smalltalk messaging to C. Some guy named Bjarne invents “C with Classes”. • 1986: Cox authors Object Oriented Programming: an evolutionary approach, ObjC is born • 1988: NeXT licence ObjC from StepStone • 1993: GCC runtime for ObjC on !NeXT OS
- 7. Memory Lane • 1980s: Brad Cox at StepStone adds Smalltalk messaging to C. Some guy named Bjarne invents “C with Classes”. • 1986: Cox authors Object Oriented Programming: an evolutionary approach, ObjC is born • 1988: NeXT licence ObjC from StepStone • 1993: GCC runtime for ObjC on !NeXT OS • 1995: NeXT purchase all ObjC rights
- 8. Memory Lane • 1980s: Brad Cox at StepStone adds Smalltalk messaging to C. Some guy named Bjarne invents “C with Classes”. • 1986: Cox authors Object Oriented Programming: an evolutionary approach, ObjC is born • 1988: NeXT licence ObjC from StepStone • 1993: GCC runtime for ObjC on !NeXT OS • 1995: NeXT purchase all ObjC rights • 1996: Apple (Computer, back then) acquire NeXT
- 9. Memory Lane • 1980s: Brad Cox at StepStone adds Smalltalk messaging to C. Some guy named Bjarne invents “C with Classes”. • 1986: Cox authors Object Oriented Programming: an evolutionary approach, ObjC is born • 1988: NeXT licence ObjC from StepStone • 1993: GCC runtime for ObjC on !NeXT OS • 1995: NeXT purchase all ObjC rights • 1996: Apple (Computer, back then) acquire NeXT • 2001: Mac OS X released
- 10. What does MVC mean?
- 11. What does MVC mean? Display information Prepare content Provide information
- 12. What does MVC mean? Respond to events Display information Trigger service logic Prepare content Do the work Provide information
- 13. Demo - one-minute browser
- 14. What did I do?
- 15. What did I do? • Drew boxes in Interface Builder
- 16. What did I do? • Drew boxes in Interface Builder • Automatically created and archived View objects
- 17. What did I do? • Drew boxes in Interface Builder • Automatically created and archived View objects • Automatically un-archived and displayed by my app
- 18. What did I do? • Drew boxes in Interface Builder • Automatically created and archived View objects • Automatically un-archived and displayed by my app • MVC score: F Should really try harder
- 19. On syntax
- 20. On syntax • [anObject sendMessage: parameter];
- 21. On syntax • [anObject sendMessage: parameter]; • @property int count; • int x = anObject.count; • anObject.count = x * 2;
- 22. Demo - model the URL
- 25. MVC Score: D Principles not really applied
- 26. Delegates
- 27. Delegates • Customise an object’s behaviour by making decisions on its behalf
- 28. Delegates • Customise an object’s behaviour by making decisions on its behalf • GoF: Template Method (kindof)
- 29. Delegates • Customise an object’s behaviour by making decisions on its behalf • GoF: Template Method (kindof) • Implement a subset of delegate methods, runtime introspection avoids exceptions
- 30. Delegates • Customise an object’s behaviour by making decisions on its behalf • GoF: Template Method (kindof) • Implement a subset of delegate methods, runtime introspection avoids exceptions • We’ll use WebFrameLoadDelegate
- 31. Demo - fix the address bar
- 32. Demo - fix the address bar (oh, and add window titles)
- 33. Cocoa Bindings
- 34. Cocoa Bindings «bind»
- 35. Cocoa Bindings «bind» «observe»
- 39. MVC Score: B Good, but I want bookmarks ☺
- 40. Demo - bookmarks
- 46. MVC Score: A That’ll do for now!
- 47. ?
Notes de l'éditeur
- Who I am. What _are_ Objective-C and Cocoa? First, a walk down memory lane.
- Objective-C was really popularised by NeXT on their NeXTSTEP OS. Note that there’s never been a language standard, but Apple owns all trademarks and drives the language definition. GCC support on other platforms plays catch-up. Next: what exactly is MVC?
- Objective-C was really popularised by NeXT on their NeXTSTEP OS. Note that there’s never been a language standard, but Apple owns all trademarks and drives the language definition. GCC support on other platforms plays catch-up. Next: what exactly is MVC?
- Objective-C was really popularised by NeXT on their NeXTSTEP OS. Note that there’s never been a language standard, but Apple owns all trademarks and drives the language definition. GCC support on other platforms plays catch-up. Next: what exactly is MVC?
- Objective-C was really popularised by NeXT on their NeXTSTEP OS. Note that there’s never been a language standard, but Apple owns all trademarks and drives the language definition. GCC support on other platforms plays catch-up. Next: what exactly is MVC?
- Objective-C was really popularised by NeXT on their NeXTSTEP OS. Note that there’s never been a language standard, but Apple owns all trademarks and drives the language definition. GCC support on other platforms plays catch-up. Next: what exactly is MVC?
- Objective-C was really popularised by NeXT on their NeXTSTEP OS. Note that there’s never been a language standard, but Apple owns all trademarks and drives the language definition. GCC support on other platforms plays catch-up. Next: what exactly is MVC?
- Objective-C was really popularised by NeXT on their NeXTSTEP OS. Note that there’s never been a language standard, but Apple owns all trademarks and drives the language definition. GCC support on other platforms plays catch-up. Next: what exactly is MVC?
- Well, we know it’s Model-View-Controller, I put that on the first slide. But what does each level do? Next: into the sample.
- Well, we know it’s Model-View-Controller, I put that on the first slide. But what does each level do? Next: into the sample.
- Well, we know it’s Model-View-Controller, I put that on the first slide. But what does each level do? Next: into the sample.
- Well, we know it’s Model-View-Controller, I put that on the first slide. But what does each level do? Next: into the sample.
- Well, we know it’s Model-View-Controller, I put that on the first slide. But what does each level do? Next: into the sample.
- Well, we know it’s Model-View-Controller, I put that on the first slide. But what does each level do? Next: into the sample.
- Well, we know it’s Model-View-Controller, I put that on the first slide. But what does each level do? Next: into the sample.
- Well, we know it’s Model-View-Controller, I put that on the first slide. But what does each level do? Next: into the sample.
- Well, we know it’s Model-View-Controller, I put that on the first slide. But what does each level do? Next: into the sample.
- Well, we know it’s Model-View-Controller, I put that on the first slide. But what does each level do? Next: into the sample.
- Well, we know it’s Model-View-Controller, I put that on the first slide. But what does each level do? Next: into the sample.
- I could do 45 of these in one session - it’s a shame there’s no market.
- So we can see how Interface Builder works, but haven’t designed an MVC app at all. FAIL. Next: see what does really count as a model.
- So we can see how Interface Builder works, but haven’t designed an MVC app at all. FAIL. Next: see what does really count as a model.
- So we can see how Interface Builder works, but haven’t designed an MVC app at all. FAIL. Next: see what does really count as a model.
- So we can see how Interface Builder works, but haven’t designed an MVC app at all. FAIL. Next: see what does really count as a model.
- So we can see how Interface Builder works, but haven’t designed an MVC app at all. FAIL. Next: see what does really count as a model.
- Brief description of the message-sending syntax and Objective-C 2.0 properties. Just enough so that the code samples make sense.
- Brief description of the message-sending syntax and Objective-C 2.0 properties. Just enough so that the code samples make sense.
- Brief description of the message-sending syntax and Objective-C 2.0 properties. Just enough so that the code samples make sense.
- Brief description of the message-sending syntax and Objective-C 2.0 properties. Just enough so that the code samples make sense.
- The only model object we really have is the URL. Let’s see how we can factor that out into an MVC design. Next: class view.
- So, we’ve separated things out, but that model object isn’t really used. The Controller is just filling it in out of a sense of duty. Next: move onto fixing the URL field, but discuss delegates first.
- So, we’ve separated things out, but that model object isn’t really used. The Controller is just filling it in out of a sense of duty. Next: move onto fixing the URL field, but discuss delegates first.
- So, we’ve separated things out, but that model object isn’t really used. The Controller is just filling it in out of a sense of duty. Next: move onto fixing the URL field, but discuss delegates first.
- So, we’ve separated things out, but that model object isn’t really used. The Controller is just filling it in out of a sense of duty. Next: move onto fixing the URL field, but discuss delegates first.
- So, we’ve separated things out, but that model object isn’t really used. The Controller is just filling it in out of a sense of duty. Next: move onto fixing the URL field, but discuss delegates first.
- Some objects implement a basic behaviour then allow another object to interpose at specific points in the process. This is called delegation in Cocoa. It’s a bit like a Template Method, except that the delegate doesn’t encapsulate the original object. ObjC messaging means you can implement a subset of the delegate methods.
- Some objects implement a basic behaviour then allow another object to interpose at specific points in the process. This is called delegation in Cocoa. It’s a bit like a Template Method, except that the delegate doesn’t encapsulate the original object. ObjC messaging means you can implement a subset of the delegate methods.
- Some objects implement a basic behaviour then allow another object to interpose at specific points in the process. This is called delegation in Cocoa. It’s a bit like a Template Method, except that the delegate doesn’t encapsulate the original object. ObjC messaging means you can implement a subset of the delegate methods.
- Some objects implement a basic behaviour then allow another object to interpose at specific points in the process. This is called delegation in Cocoa. It’s a bit like a Template Method, except that the delegate doesn’t encapsulate the original object. ObjC messaging means you can implement a subset of the delegate methods.
- We can use a delegation point in the loading of a web page in order to get the address that the web view has really gone to. Oh, where’s the code to update the text field, though?
- If a view (say) binds to a model, then the model is actually replaced by a proxy which posts observer notifications whenever changes are requested. Next: how that works in the browser app.
- If a view (say) binds to a model, then the model is actually replaced by a proxy which posts observer notifications whenever changes are requested. Next: how that works in the browser app.
- If a view (say) binds to a model, then the model is actually replaced by a proxy which posts observer notifications whenever changes are requested. Next: how that works in the browser app.
- If a view (say) binds to a model, then the model is actually replaced by a proxy which posts observer notifications whenever changes are requested. Next: how that works in the browser app.
- If a view (say) binds to a model, then the model is actually replaced by a proxy which posts observer notifications whenever changes are requested. Next: how that works in the browser app.
- If a view (say) binds to a model, then the model is actually replaced by a proxy which posts observer notifications whenever changes are requested. Next: how that works in the browser app.
- So apart from triggering the “go” operation, the text field and web view are entirely decoupled. The model now has some utility. Next: bookmarks.
- So apart from triggering the “go” operation, the text field and web view are entirely decoupled. The model now has some utility. Next: bookmarks.
- So apart from triggering the “go” operation, the text field and web view are entirely decoupled. The model now has some utility. Next: bookmarks.
- So apart from triggering the “go” operation, the text field and web view are entirely decoupled. The model now has some utility. Next: bookmarks.
- So apart from triggering the “go” operation, the text field and web view are entirely decoupled. The model now has some utility. Next: bookmarks.
- So apart from triggering the “go” operation, the text field and web view are entirely decoupled. The model now has some utility. Next: bookmarks.
- Add the bookmarks. No need to change the model, just bind the new UI to a collection of web addresses.
- First: NSArrayController manages its content Second: Add bookmark, note how information only passed over the controller layer Third: Bookmark this page, again information flow over controller layer only Next: Qs!
- First: NSArrayController manages its content Second: Add bookmark, note how information only passed over the controller layer Third: Bookmark this page, again information flow over controller layer only Next: Qs!
- First: NSArrayController manages its content Second: Add bookmark, note how information only passed over the controller layer Third: Bookmark this page, again information flow over controller layer only Next: Qs!
- First: NSArrayController manages its content Second: Add bookmark, note how information only passed over the controller layer Third: Bookmark this page, again information flow over controller layer only Next: Qs!
- First: NSArrayController manages its content Second: Add bookmark, note how information only passed over the controller layer Third: Bookmark this page, again information flow over controller layer only Next: Qs!
- First: NSArrayController manages its content Second: Add bookmark, note how information only passed over the controller layer Third: Bookmark this page, again information flow over controller layer only Next: Qs!
- First: NSArrayController manages its content Second: Add bookmark, note how information only passed over the controller layer Third: Bookmark this page, again information flow over controller layer only Next: Qs!
- First: NSArrayController manages its content Second: Add bookmark, note how information only passed over the controller layer Third: Bookmark this page, again information flow over controller layer only Next: Qs!
- First: NSArrayController manages its content Second: Add bookmark, note how information only passed over the controller layer Third: Bookmark this page, again information flow over controller layer only Next: Qs!