Operators, String Interpolation, Arrays
Welcome to the next segment of my posts.
Operators
You can make Swift, or any programming language in general, do cool things.
var a = 10
b = a + 2
c = a - 2
d = a * 2
e = a / 2
print(b, c, d, e); // that'd say 12, 8, 20 and 5, respectively.
If you know math, this should be straightforward. You can even do squared calculations.
There are also comparison operators, like >, <, <=, >=, ==. In programming, however, do not use ”=” as an equality operator. It is reserved for assigning variables and constants. Use ”==” instead.
String Interpolation
By the way, some operators work with strings too.
var test = "Hello "
var test2 = " world!"
var test3 = test + test2
print(test3) // "Hello world!"
If you have a variable or constant of some kind and you want to display it in a String, use the String Interpolation technique. It sounds scary, but all you have to do is:
var thing = 10
print(Thing is \(thing))
You put the variable/constant that you want to be displayed in the string in parentheses “()” and add a backslash character - ”". Anything between the string interpolation can be an operator. So you can do calculations like:
var age = 10
print (You are \(age) years old. You will be \(age+1) next year.
Swift is smart like that.
Arrays
Arrays are collections of data. They usually look like this:
var array = ["a", "b", "c"]
Brackets are used to mark the start and end of an array, and each item is seperated by a comma. You can access items in arrays by typing the array name along with brackets and the index of the item you want.
However, computers count arrays from 0 and not 1. So, in an array of 5 items, the max index is 4.
var array = ["a", "b", "c"]
print array[0] // "a"
To create your own array, type the name of the array, and then wrap its type (the type of its contents) in brackets, then finally put parentheses after that.
var array: [String]()
If you are coming from another language, Swift doesn’t let you declare the array first and then add things to it later.
var newArray: [String]
newArray[0] = "a" // doesn't work
When you use var array: [String], Swift simply knows that there’s going to be an array named newArray that will store strings, and doesn’t actually create it until later. To make the array, use the technique(syntax) above.
You can also use operators on arrays. You can merge 2 arrays with “+”:
var array1 = ["a", "b", "c"]
var array2 = ["d", "e", "f"]
var array3 = array1 + array2
print(array3) // ["a", "b", "c", "d", "e", "f"]
I think that should be enough for now. See you later, Nắng Trong Vườn