Swift Basics

Swift’s icon is like a swallow which is flying! Follow me, learn swift one by one, I believe we can fly!

(sort out it by internet,any similarity is purely coincidental)

Someday, I might add translations(😀😀😀😀😀).

Begin One : swift basics

We just created a variable, called it name and gave it a value. Variables are created with the keyword 'var', followed by a name and a value, which is assigned with '='

var task = "learn java"
task = "learn swift"
print(task)  ==>  learn swift

Just like I cant't handle more than one of these tasks at once, variables can only remember one value at a time.
If you want to give your variable a different value, simply use its name (without 'var')

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Programs are written in code. That's another word for lists of instructions. With code, we can build great apps, games and websites. Sit tight, Let's look at the following:

var love = "I love"
var cookies = "peanut biscuit"
print(love + cookie + "!")  ==>  I love peanut biscuit!

The word print followed by '( )' reveals the output, specified by the string inside the brackets.
Psst:print( ) is called a function

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Variables can store lots of different things. We've already seen that we can store strings. But wait : numbers can be stored as well!

var myString = "4"
var myNumber = 4

We can see: myString holds a string and myNumber has the value 4.
It's important to notice that there's a difference. If you want a variable to hold a meaningful value, just use a number without "quotation marks".

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Numbers come in different types. Integers can hold whole numbers, Doubles can hold numbers with a decimal place.
If you assign a number to a variable, the variable automatically knows which type of number it can hold.

var myInteger = 2
var myDouble = 2.0
myInteger = 10(正确)
myInteger = "10"(X)
myInteger = 10.0(X)

The variable myInteger has the value 2 assigned to it. From now on, it will only take Integer values. "10"(string) and 10.0(Double) won't work.

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With code, we can also do math!

var five = 5
var six = 6
var result = five + six
print(result)  ==>  11

We can do basic math operations with '+', '-', '*', '/'. Our beloved print( ) function doesn't just work with strings but with numbers as well!

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We can change the values of variables at any time. If we know that the value of a variable won't change, it's a good idea ti use let instead
My name is 'dabaodeaiqing' and I sure hope that'll stay this way. so:

let name = "dabaodeaiqing"

then my name is a constant and can't be tinkered with!

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If we don't want to assign a value to a variable upon creation, the variable doesn't know what type of data it can hold. In that case, we need to give the variable a type.

var myString: String
var myInteger: Int
var myDouble: Double

We've created three variables that can hold three different types of data. Stay tuned, we''ll talk about many more types in Swift!

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We've already learned a lot about programming. We know how variables are created, what the difference between var and let is, how to combine strings and how to peint something out.

var numberVar = 42
var stringVar: String
let pt1 = "Let's learn swift"
let pt2 = "happily!"
var output = pt1 + pt2
print(output)  ==>  Let's learn swift happily!

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Thanks a lot!