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Little lessons learned from Swift
The document discusses key lessons learned while transitioning from Objective-C to Swift, emphasizing the power of switch statements compared to if statements for clearer code intent. It also addresses the concept of optionals in Swift, highlighting their nature as enums and the importance of safe unwrapping. Additional topics include using computed properties, delegates, and functional array operations.
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Little lessons learned from Swift
- 1. Little lessons learned fromSwift Very first steps after transitioning from Objective-C
- 2. Switch switch is muchmore powerful in Swift than in Obj-C You can replace lots of if statements by switch statements
- 3. Even if you’reable to do something with a single if statement, sometimes it has much more sense to think of a switch instead, for example: Switch
- 4. Advantage Code intention isclearer, it tells you that you have (or might have) more options to switch over. With a single if, you don’t realize that. Switch
- 5. When you combinethe powerful of switch with enums, you are working on the base of the Pattern Matching concept. case .Delayed(let minutes) println("delayed by (minutes) minutes” Switch & Enum
- 6. Table view sections Interestinguse case “raw” type = 0 = 1 = 2 // implicit // raw // values toRaw fromRaw Switch & Enum
- 7. A very interestinguse case of Pattern Matching in our world is for completion functions… Another interesting use case Completion is a type. .Success with Array<T> .Failure with NSError … or … Switch & Enum
- 8. Switch & Enum *switchesin Swift don’t fall through automatically
- 9. It takes afunction as argument, whose argument is a Completion type. The function is executed here, passing a .Success case with an array of Contributions. Switch & Enum
- 10. It takes afunction as argument, whose argument is a Completion type. The function is executed here, passing a .Success case with an array of Contributions. Computed property Switch & Enum
- 11. Computed Properties // processwhatever you need // in order to return the array
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- 16. Optionals An optional isa type
- 17. Optionals An optional isa type An optional is actually an enum, so that:
- 18. Optionals An optional isa type An optional is actually an enum, so that:
- 19. Optionals An optional isa type An optional is actually an enum, so that:
- 20. Optionals An optional isa type An optional is actually an enum, so that:
- 21. Optionals An optional isa type An optional is actually an enum, so that:
- 22. Optionals String? “A Stringthat can be nil”
- 23. Optionals String? “A Stringthat can be nil”
- 24. Optionals String? “A Stringthat can be nil” An Optional that can be a String
- 25. Optionals String? “A Stringthat can be nil” An Optional that can be a String …or can eventually be nil
- 26. Optionals String? “A Stringthat can be nil” An Optional that can be a String …or can eventually be nil String? String nil
- 27. Optionals String? “A Stringthat can be nil” An Optional that can be a String …or can eventually be nil String? String nil stringThatCanBeNil // not a String, but a String?
- 28. Optionals String? “A Stringthat can be nil” An Optional that can be a String …or can eventually be nil String? String nil stringThatCanBeNil // not a String, but a String? stringThatCanBeNil! // The ! operator "unwraps" the optional, // you get String then
- 29. Optionals But… warning! If youtry to unwrap an optional and it happens to be nil, the app will crash!
- 30. Optionals But… warning! If youtry to unwrap an optional and it happens to be nil, the app will crash!
- 31. Optionals So, should weuse the unwrapping (!) operator…?
- 32. Optionals So, should weuse the unwrapping (!) operator…? Well, yes (in some cases)… Because sometimes we do want the app to crash!
- 33. Optionals So, should weuse the unwrapping (!) operator…? Well, yes (in some cases)… Because sometimes we do want the app to crash! Example:
- 34. Optionals So, should weuse the unwrapping (!) operator…? Well, yes (in some cases)… Because sometimes we do want the app to crash! Example:
- 35. Optionals So, should weuse the unwrapping (!) operator…? Well, yes (in some cases)… Because sometimes we do want the app to crash! Example: Will return TransactionCell if possible, nil otherwise
- 36. Optionals So, should weuse the unwrapping (!) operator…? Well, yes (in some cases)… Because sometimes we do want the app to crash! Example: Will return TransactionCell if possible, nil otherwise
- 37. Optionals So, should weuse the unwrapping (!) operator…? Well, yes (in some cases)… Because sometimes we do want the app to crash! Example: Will return TransactionCell if possible, nil otherwise
- 38. Optionals amount is String? valueis String // value doesn’t need to be unwrapped "if let" unwraps variables automatically
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- 42. Optionals The ?? operator leta: Int? let b: Int let result: Int
- 43. Optionals The ?? operator iflet value = a { result = value } else { result = b } let a: Int? let b: Int let result: Int
- 44. Optionals The ?? operator iflet value = a { result = value } else { result = b } result = a ? a! : b let a: Int? let b: Int let result: Int
- 45. Optionals The ?? operator result= a ?? b if let value = a { result = value } else { result = b } result = a ? a! : b let a: Int? let b: Int let result: Int
- 46. Tips A good placeto set a delegate How to declare constants in your class
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- 48. Tips Interesting piece ofcode Defining a computed property
- 49. Tips Interesting piece ofcode Define constants Defining a computed property
- 50. Tips Interesting piece ofcode Define constants Using as? Defining a computed property
- 51. Tips Interesting piece ofcode Define constants Using as? Defining a computed property Using ?? operator
- 52. Syntax Sugar // initializednil by default // initialized nil by default
- 53. self.property vs property <<the debate >>
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