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Golang basic: Variable and data type

shellrean profile image ShellRean Updated on ・2 min read

variable is a container of value, what type value of you want to assign is data type. golang is static typing that mean you have to ensure what type actually you want to assign to the variable.

Data type Go

There is several data types

  • int
  • string
  • bool

int is data type numeric the value is number without floating point like -90,89,...,0,89,90.

string is data type text the value is text and phrase or word like "Steve", "Hello World", "I love learning golang".

bool is data type logic containt just 2 variant value true or false.

Declare variable

There is two way to create variable

package main

import "fmt"

func main() {
    var name string
    var age int
    var graduates bool

    name = "Linda"
    age = 24
    graduates = false

    fmt.Printf("%s and i %d years old", name, age)
    fmt.Println(graduates)

    // OR
    name1 := "Linda"
    fmt.Println(name1)
}
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The first way, declare first variable name using key var and following string as data type so the format is look like.
var variable_name <data_type>

The second one is using := to declare variable and assign value, data type will follow the value. From the example we assign "Linda" so variable name1 will have string data type.

Symbol := just can be using once, you will get error if you using it at the same variable name. So if you want to change value of name1 just write name = "Linda changed"

package main

import "fmt"

func main() {
    name1 := "Linda" // Will set variable name1 as string 
    fmt.Println(name1)

    name1 = "Linda changed"
    fmt.Println(name1)
}
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Go is static typing, int value can't assign to variable name1 cause name1 as string, it will show you compiler error.

package main

import "fmt"

func main() {
    name1 := "Linda"
    name1 = 1
    // Compiler error
    fmt.Println(name)
}
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All variable that you have declared have to use, if there is a variable that never use, it will get out error compiler

package main

import "fmt"

func main(){
    name := "Steve"
    age := 17
    married := false

    fmt.Println(name)
    fmt.Println(age)
}
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It will show you error because the variable married never been used. Not only variable the rule is same with package, if you import package for example fmt, you have use it or you can get error compiler.

Conclusion

We have knew how to create variable and data type so now you can specify what kind of data type you need.

Question:
Why we assign age as int why not string?

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