Go

Golang: switch statement with fallthrough

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Go only runs the selected case, not all the cases that follow. In effect, the break statement that is needed at the end of each case in those languages is provided automatically in Go.

package main

import (
	"fmt"
)

func main() {
	var age int = 29
	switch {
	case age < 25:
		fmt.Println("age is less than 25")
		fallthrough
	case age < 30:
		fmt.Println("age is less than 30")
		fallthrough
	case age < 35:
		fmt.Println("age is less than 35")
	case age < 40:
		fmt.Println("age is less than 40")
	}
}

Output

age is less than 30
age is less than 35

使用上請注意不能在最後一個 case 使用 fallthrough 不然會發生錯誤。

cannot fallthrough final case in switch
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Go

Golang: using pointers in for-range loop

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You can achieve the same effect without a function though: just create a local copy and use the address of that:

for _, each := range arr {
    each2 := each
    err := ds.repo.Insert(&each2)
    // ...
}

Also note that you may also store the address of the slice elements:

for i := range arr {
    err := ds.repo.Insert(&arr[i])
    // ...
}

Solve “using a reference for the variable on range scope `xxxx` (scopelint)” error.

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Go

Golang: convert between int, int64 and string

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int to string

s := strconv.Itoa(123)

int64 to string

var n int64 = 123
s := strconv.FormatInt(n, 10) // s == "123" (decimal)

var n int64 = 123
s := strconv.FormatInt(n, 16) // s == "7b" (hexadecimal)

string to int

s := "123"
n, err := strconv.Atoi(s)

string to int64

s := "123"
n, err := strconv.ParseInt(s, 10, 64)
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