1. Introduction
1. what you will learn
2. Introduction
2. Golang In Windows
3. Golang In Linux
4. Variables
变量: 用变量名指向一段内存空间((堆)), 变量类型指定了变量的所指向的空间大小
1. Variables Concept
2. Var Keyword Declaration - When the Type is Removed
package main
import "fmt"
func main() {
var variable1 = 100
var variable2 = "Go programming Language"
var variable3 = 114.514
fmt.Printf("The Value of Variable 1: %d\n", variable1)
fmt.Printf("The Type of Variable 1: %T\n", variable1)
fmt.Printf("The Value of Variable 2: %s\n", variable2)
fmt.Printf("The Type of Variable 2: %T\n", variable2)
fmt.Printf("The Value of Variable 3: %f\n", variable3)
fmt.Printf("The Type of Variable 3: %T\n", variable3)
}
3. Var Keyword Declaration - When the Expression is Removed
package main
import "fmt"
func main() {
// 没给初始值会赋予默认值(零值)
var variable1 int // 0
var variable2 string //
var variable3 float64 // 0.000000
fmt.Printf("The Value of Variable 1: %d\n", variable1)
fmt.Printf("The Value of Variable 2: %s\n", variable2)
fmt.Printf("The Value of Variable 3: %f\n", variable3)
}
4. Var Keyword Declaration - Multiple Variables of the Same Type
package main
import "fmt"
func main() {
//var variable1, variable2, variable3 = 2, 456, 67
var variable1, variable2, variable3 int = 2, 456, 67
fmt.Printf("The Value of Variable 1: %d\n", variable1)
fmt.Printf("The Value of Variable 2: %d\n", variable2)
fmt.Printf("The Value of Variable 3: %d\n", variable3)
}
5. Var Keyword Declaration - Multiple Variables of Different Types
package main
import "fmt"
func main() {
var variable1, variable2, variable3 = 2, "Golang", 34.56
fmt.Printf("The Value of Variable 1: %d\n", variable1)
fmt.Printf("The Type of Variable 1: %T\n", variable1)
fmt.Printf("The Value of Variable 2: %s\n", variable2)
fmt.Printf("The Type of Variable 2: %T\n", variable2)
fmt.Printf("The Value of Variable 3: %f\n", variable3)
fmt.Printf("The Type of Variable 3: %T\n", variable3)
}
6. Var Keyword Declaration - Default Value
package main
import "fmt"
func main() {
var num1 float32 // 0
var num2 int32 // 0
var firstname string //
var married bool // false
fmt.Println(num1)
fmt.Println(num2)
fmt.Println(firstname)
fmt.Println(married)
}
7. Var Keyword Declaration - Variables Declaration Block
package main
import "fmt"
func main() {
var (
firstname = "Kim"
num1 = 300
num2 = 20.65
married = true
)
fmt.Println(firstname)
fmt.Println(num1)
fmt.Println(num2)
fmt.Println(married)
}
8. Short Variables - Declaration and Initialization
package main
import "fmt"
func main() {
var1 := 100
var2 := "go programming"
var3 := 135.94
fmt.Printf("The Value of Var 1: %d\n", var1)
fmt.Printf("The Type of Var 1: %T\n", var1)
fmt.Printf("The Value of Var 2: %s\n", var2)
fmt.Printf("The Type of Var 2: %T\n", var2)
fmt.Printf("The Value of Var 3: %f\n", var3)
fmt.Printf("The Type of Var 3: %T\n", var3)
}
9. Short Variables - Multiple Variables of Same and Different Types
same type
package main
import "fmt"
func main() {
var1, var2, var3 := 100, 200, 300
fmt.Printf("The Value of Var 1 : %d\n", var1)
fmt.Printf("The Type of Var 1 : %T\n", var1)
fmt.Printf("The Value of Var 2 : %d\n", var2)
fmt.Printf("The Type of Var 2 : %T\n", var2)
fmt.Printf("The Value of Var 3 : %d\n", var3)
fmt.Printf("The Type of Var 3 : %T\n", var3)
}
multiple type
package main
import "fmt"
func main() {
//s variable declaration by declare multiple variables by differents type in single line
var1, var2, var3 := 300, "GO Programming", 86.54
fmt.Printf("The Value of Var 1 : %d\n", var1)
fmt.Printf("The Type of Var 1 : %T\n", var1)
fmt.Printf("The Value of Var 2 : %s\n", var2)
fmt.Printf("The Type of Var 2 : %T\n", var2)
fmt.Printf("The Value of Var 3 : %f\n", var3)
fmt.Printf("The Type of Var 3 : %T\n", var3)
}
10. Scope of Variables
define variable
package main
import "fmt"
func main() {
//declare local variables
var variable1, variable2 int = 100, 200
fmt.Printf("Variable1 Value is : %d\n", variable1)
fmt.Printf("Variable2 Value is : %d ", variable2)
}
define global and local variable
package main
import "fmt"
var golobalVariable int = 100
func main() {
//local variable scope starts
var localVariable int = 200
fmt.Printf("Global Variable is %d\n", golobalVariable)
fmt.Printf("Local Variable : %d\n", localVariable)
display()
// local variable scope ends
}
func display() {
fmt.Printf("The Value of Global variable is %d", golobalVariable)
}
define global and local same name variable
package main
import "fmt"
var variable1 int = 500
func main() {
var variable1 int = 200
fmt.Printf("Global Variable is %d\n", variable1) // 200
}
