Little lessons learned from Swift

Very first steps after transitioning from Objective-C

Switch

switch is much more powerful in Swift than in Obj-C

You can replace lots of if statements by switch statements

Even if you’re able to do something with a single if statement, sometimes it has much more sense to think of a switch

instead, for example:

Switch

Advantage

Code intention is clearer, it tells you that you have (or might have) more options to switch over.

With a single if, you don’t realize that.

Switch

When you combine the 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

Table view sections

Interesting use case

“raw” type

= 0= 1= 2

// implicit // raw // values

toRaw

fromRaw

Switch & Enum

A very interesting use 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

Switch & Enum

*switches in Swift don’t fall through automatically

It takes a function as argument, whose argument is a Completion type.

The function is executed here, passing a .Success case with an array of Contributions.

Switch & Enum

It takes a function 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

Computed Properties

// process whatever you need // in order to return the array

Computed Properties

Computed Properties

Computed Properties

Optionals

OptionalsAn optional is a type

OptionalsAn optional is a type

An optional is actually an enum, so that:

OptionalsAn optional is a type

An optional is actually an enum, so that:

OptionalsAn optional is a type

An optional is actually an enum, so that:

OptionalsAn optional is a type

An optional is actually an enum, so that:

OptionalsAn optional is a type

An optional is actually an enum, so that:

OptionalsString? “A String that can be nil”

OptionalsString? “A String that can be nil”

OptionalsString? “A String that can be nil”

An Optional that can be a String

OptionalsString? “A String that can be nil”

An Optional that can be a String

…or can eventually be nil

OptionalsString? “A String that can be nil”

An Optional that can be a String

…or can eventually be nil

String?

Stringnil

OptionalsString? “A String that can be nil”

An Optional that can be a String

…or can eventually be nil

String?

Stringnil stringThatCanBeNil

// not a String, but a String?

OptionalsString? “A String that can be nil”

An Optional that can be a String

…or can eventually be nil

String?

Stringnil stringThatCanBeNil

// not a String, but a String?

stringThatCanBeNil!// The ! operator "unwraps" the optional, // you get String then

OptionalsBut… warning!

If you try to unwrap an optional and it

happens to be nil, the app will crash!

OptionalsBut… warning!

If you try to unwrap an optional and it

happens to be nil, the app will crash!

OptionalsSo, should we use the unwrapping (!) operator…?

OptionalsSo, should we use the unwrapping (!) operator…?

Well, yes (in some cases)… Because sometimes we do want the app to crash!

OptionalsSo, should we use the unwrapping (!) operator…?

Well, yes (in some cases)… Because sometimes we do want the app to crash!

Example:

OptionalsSo, should we use the unwrapping (!) operator…?

Well, yes (in some cases)… Because sometimes we do want the app to crash!

Example:

OptionalsSo, should we use 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

OptionalsSo, should we use 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

OptionalsSo, should we use 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

Optionals

amount is String?

value is String

// value doesn’t need to be unwrapped

"if let" unwraps variables automatically

OptionalsObj-C

OptionalsObj-C

Swift

OptionalsThe ?? operator

OptionalsThe ?? operator

let a: Int?let b: Intlet result: Int

OptionalsThe ?? operator

if let value = a { result = value } else { result = b }

let a: Int?let b: Intlet result: Int

OptionalsThe ?? operator

if let value = a { result = value } else { result = b }

result = a ? a! : b

let a: Int?let b: Intlet result: Int

OptionalsThe ?? operator

result = a ?? b

if let value = a { result = value } else { result = b }

result = a ? a! : b

let a: Int?let b: Intlet result: Int

TipsA good place to set a delegate

How to declare constants in your class

TipsInteresting piece of code

TipsInteresting piece of code

Defining a computed property

TipsInteresting piece of code

Define constants

Defining a computed property

TipsInteresting piece of code

Define constants

Using as?

Defining a computed property

TipsInteresting piece of code

Define constants

Using as?

Defining a computed property Using ?? operator

Syntax Sugar

// initialized nil by default

// initialized nil by default

self.property vs property

<< the debate >>

self.property vs propertyhttp://stackoverflow.com/questions/24215578/when-should-i-access-properties-with-self-in-swift

Fun with arrays!

sort

filter

map

reduce

Fun with arrays!