Complete Guid for the new programming language 'Swift' for developing apps for iOS and OS X. Swift is an alternative for Objective-C language.

1. By: Hossam Ghareeb
hossam.ghareb@gmail.com
Part 1
The Complete Guide For
Programming Language

2. Contents.
● About Swift
● Hello World! with playground
● Variables & Constants
● Printing Output
● Type Conversion
● If
● If with optionals
● Switch
● Switch With Ranges.
● Switch With Tuples.
● Switch With Value Binding
● Switch With "Where"
● Loops
● Functions
● Passing & Returning Functions
● Closures (Blocks)
● Arrays
● Dictionaries
● Enum

3. About Swift
● Swift is a new scripting programming language for iOS and OS X
apps.
● Swift is easy, flexible and funny.
● Unlike Objective-C, Swift is not C Compatible. Objective-C is a
superset of C but Swift is not.
● Swift is readable like Objective-C and designed to be familiar to
Objective-C developers.
● You don't have to write semicolons, but you must write it if you
want to write multiple statements in single line.
● You can start writing apps with Swift language starting from
Xcode 6.
● Swift doesn't require main function to start with.

4. Hello World!
As usual we will start with printing "Hello World" message. We will
use something called playground to explore Swift language. It's an
amazing tool to write and debug code without compile or run.
Create or open an Xcode project
and create new playground:

5. Hello World!
Use "NSLog" or "println" to print message to console. As you see in
the right side you can see in real time the values of variables or
console message.

6. Variables & Constants.
In Swift, use 'let' for constans and 'var' for variables. In constants you
can't change the value of a constant after being initialized and you
must set a value to it.
Although you use 'var' or 'let' for variables, Swift is typed language.
The type is written after ':' . You don't have to write the type of
variable or constant because the compiler will infer it using its initial
value.
BUT if you didn't set an initial value or the initial value that you
provided is not enough to determine the type, you have to explicitly
type the variable or constants.
Check examples:

7. Variables & Constants.

8. Variables & Constants.
In Objective-C we used to use mutability, for example:
NSArray and NSMutableArray or NSString and NSMutableString
In Swift, when you use var, all objects will be mutable BUT when you
use let, all objects will be immutable:

9. Printing Output
● We introduced the new way to print output using println(). Its
very similar to NSLog() but NSLog is slower, adds timestamp to
output message and appear in device log. Println() appear in
debugger log only.
● In Swift you can insert values of variables inside String using "()" a
backslash with parentheses, check example:

10. Type Conversion
Swift is unlike other languages, it will not implicitly convert types of
result of statements. Lets check example in Obj-C :
In Swift you can't do this. You have to decide the type of result by
explicitly converting it to Double or Integer. Check next example:

11. Type Conversion
Here we should convert any one of them so the two variables be in same
type.
Swift guarantees safety in your code and makes you decide the type of
your result.

12. If
● In Swift, you don't have to add parentheses around the condition.
But you should use them in complex conditions.
● Curly braces { } are required around block of code after If or else.
This also provide safety to your code.

13. If
● Conditions must be Boolean, true or false. Thus, the next code
will not work as it was working in Objective-C :
As you see in Swift, you cannot check in variable directly like
Objective-C.

14. If With Optionals
● You can set the variable value as Optional to indicate that it may
contain a value or nil.
● Write question mark "?" after the type of variable to mark it as
Optional.
● Think of it like the "weak" property, it may point to an object or nil
● Use let with If to check the Optional value. If the optional value is
nil, the conditional will be false. OtherWise, the it will be true and
the value will be assigned to the constant of let
Check example:

15. If With Optionals

16. Switch
Switch works in Swift like many other languages but with some new
features and small differences:
● It supports any kind of data, not only Integers. It checks for
equality.
● Switch statement must be exhaustive. It means that you have to
cover (add cases for) all possible values for your variable. If you
can't provide case statement for each value, add a default
statement to catch other values.
● When a case is matched in switch, the program exits from the
switch case and doesn't continue checking next cases. Thus, you
don't have to explicitly break out the switch at the end of each
case.
Check examples:

17. Switch

18. Switch Cont.
● As we said, there is no fallthrough in switch statements and
therefore break is not required. So code like this will not work in
Swift:
● As you see, each case must contain at least one executable
statement.
● Multiple matches for single case can be separated by commas and
no need for fallthrough cases

19. Switch Cont.

20. Switch With Ranges.
● In Swift you can use the range of values for checking in case
statements. Ranges are identified with "..." in Swift :

21. Switch With Tuples.
Tuples are used to group multiple values in a single compound value.
Each value can be in any type. Values can be with any number as you
like:
You can decompose the values of tuples with many ways as you will
see in examples. Most of time, tuples are used to return multiple
values from function. Also can be use to enumerate dictionary
contents as (key, value). Check examples:

22. Switch With Tuples.
● Decomposing:
● Use underscore "_" to ignore parts:

23. Switch With Tuples.
● You can use element index to access tuple values. Also you can
name the elements and access them by name:
● With dictionary:

24. Switch With Tuples.
Using tuples with functions:

25. Switch With Tuples.
Now we will see tuples with switch. We will use it in checking that a
point is located inside a box in grid. Also we want to check if the point
located on x-axis or y-axis. Here is the gird:

26. Switch With Tuples.

27. Switch With Value Binding
You can bind the values of variables in switch case statements to
temporary constants to be used inside the case body:

28. Switch With "Where"
"Where" is used with case statement to add additional condition.
Check these examples:

29. Switch With "Where"
Another example in using "Where":

30. Loops
● Like other languages, you can use for and for-in loops without
changes. But in Swift you don't have to write the parentheses.
● for-in loops can iterate any collection of data. Also It can be used
with ranges

31. Functions
● Functions are created using the keyword 'func'.
● Parentheses are required for functions that don't take params.
● In parameters you type the name and type of variable between ':'
● You can describe or name the local variables of function like
Objective-C by writing the name before the local variable OR add
'#' if the local variable is already an appropriate name. Check
examples:

32. Functions
● Using names for local variables

33. Functions
● In Swift, params are considered as constants and you can't change
them.
● To change local variables, copy the values to other variables OR
tell Swift that this value is not constant by writing 'var' before the
name:

34. Functions
● To return values, you have to write the type of returned info after
'()' and "->". Use tuples to return multiple values at once.
● In Swift, you can use default parameter values. BUT be aware that
when you wanna use function with default-valued params, you
must write the name of the argument when you wanna use it.
Check examples:

35. Functions
● Using default parameter value:
● Functions can take variable number of arguments using '...' :

36. Passing & Returning Functions
● In Swift, functions are first class objects. Thus they can be passed
around
● Every function has type like this:
● You can pass a function as parameter or return it as a result.
Check examples:

37. Passing & Returning Functions

38. Closures
● Closures are very similar to blocks in C and Objective-C.
● Closures are first class type so it can be nested , returned and
passed as parameter. (Same as blocks in Objective-C)
● Functions are special cases of closures.
● Closures are enclosed in curly braces { } , then write the function
type (arguments) -> (return type), followed by in keyword that
separate the closure header from the body.

39. Closures
● Example #1, using map with an array. map returns an array with
result of each item

40. Closures
● Example #2 of using closure as completion handler when sending
api request

41. Closures
● Example #3, using the built-in "sorted" function to sort any
collection based on a closure that will decide the compare result
of any two items

42. Arrays
● Arrays in Swift are typed. You have to choose the type of array,
array of Integers, array of Strings,....etc. That's different from
Objective-C where you can create array with items of any type.
● You can write the type of array between square brackets [ ] OR If
you initialized it with data, Swift will infer the type of array
implicitly.
● Arrays by default are mutable arrays, except if you defined it as
constant using 'let' it will be immutable.
● Length of array can be know by .count property, and you can
check if is it empty or not by .isEmpty property.

43. Arrays
● Creating and initializing array is easy. Also you can create array
with certain size and default value for items:
● For appending items, use 'append' method or "+=" :

44. Arrays
● You can retrieve and update array using subscript syntax. You will
get runtime error if you tried to access item out of bound.

45. Arrays
● You can easily iterate over an array using 'for-in' , 'for' or by
'enumerate'. 'enumerate' gives you the item and its index during
enumeration.

46. Dictionaries
● Dictionary in Swift is similar to one in Objective-C but like Array,
Dictionary is strongly typed, all keys must be in same type and all
values must be in same type.
● Type of Dictionary is inferred by initial values or you have to write
the type between square brackets [ KeyType, ValueType]
● Like Arrays, Dictionaries by default are mutable dictionaries,
except if you defined it as constant using 'let' it will be immutable.
● Check examples :)

47. Dictionaries

48. Enum
● Enum is very popular concept if you have specific values of
something.
● Enum is created by the keyword 'enum' and listing all possible
cases after the keyword 'case'

49. Enum
● Enum can be used easily in switch case but as we know that switch
in Swift is exhaustive, you have to list all possible cases.

50. Enum With Associated Values
● Enum values can be used with associated values. Lets explain with
an example. Suppose you describe products in your project, each
product has a barcode. Barcodes have 2 types (UPC, QRCode)
● UPC code can be represented by 4 Integers (4,88581,01497,3),
and QR code can be represented by String ("ABCFFDF")

51. Enum With Associated Values
● So we need to represent the barcode with two condition UPC and
QR , each one has associated values to give full information.

52. Enum With Raw Values
● For sure in some cases you need to define some constants in
enum with their values. For example the power of monster has
different values based on game level (easy = 50, medium = 60,
hard = 80, very hard = 120) and these values are constant. So you
need to make enum for power values and in same time save these
values. You can create enum with cases values but they must be in
same type and this type is written after enum name. Also you can
use .rawValue to get the constant value.
● You can initialize an enum value using its constant value using this
format EnumName(rawValue: value). It returns the enum that
map to the given value. Be careful because the value returned is
Optional, it may contain an enum or nil, BECAUSE Swift can
guarantee that the given constant is exist in enum or not.

53. Enum With Raw Values Example:

54. Enum With Raw Values Example:
● Raw values can be Strings, Chars, Integers or floating point
numbers. In using Integers as a type for raw values, if you set a
value of any case, others auto_increment if you didn't specify
values for them.

55. Thanks
We have finished Part 1.
In next parts we will talk about Classes, Structures, OOP and some
advanced features of Swift.
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