整理

  1. go build yu.go
    建立exe檔案
    ./yu
    執行檔案

  2. go run main.go
    於commandline 執行檔案做測試

  3. go doc fmt
    查看套件用法
    go doc fmt.Println
    查看此套件中的方法用法

  4. const earthsGravity = 9.80665
    定義常數變數

  5. amount, unit := 10, "doll hairs"
    可以同時定義兩個變數且不同型態

  6. 空字串、空數字

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package main
import "fmt"

func main() {
  var emptyString string
  var emptyInteger integer

  fmt.Println(emptyString)
  fmt.Println(emptyInteger)

  // 
  // 0
}
  1. Println vs Print
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package main

import "fmt"

func main() {
  fmt.Println("Let's first see how", "the Println() method works.")
  fmt.Println("There's also a default space")
  
  fmt.Print("Print", "is", "different")
  fmt.Print("See?")

  /*
    Let's first see how the Println() method works.
    There's also a default space between the string arguments.
    PrintisdifferentSee?
  */

}
  1. 使用 %v, use Printf
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package main

import "fmt"

func main() {
  animal1 := "cat"
  animal2 := "dog"
  
  fmt.Printf("Are you a %v or a %v person?", animal1, animal2)

  // Are you a cat or a dog person?
}

  1. %T is Type
  2. %d is integer
  3. %f is float, ex: 3.500000
  4. %.2f is float, ex: 3.50
  5. 使用Sprintln 帶入參數並利用 Println印出字串
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package main

import "fmt"

func main() {
  step1 := "Breathe in..."
  step2 := "Breathe out..."
  
  fmt.Sprintln(step1, step2)
  
}
  // doesn't print anything

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package main

import "fmt"

func main() {
  step1 := "Breathe in..."
  step2 := "Breathe out..."
  
  meditation := fmt.Sprint(step1, step2)
  fmt.Println(meditation)
}
  // Breathe in...Breathe out...

  1. .Scan() to get user input
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package main

import "fmt"

func main() {
  fmt.Println("What would you like for lunch?")
  
  var food string
  fmt.Scan(&food)
  
  fmt.Printf("Sure, we can have %v for lunch.", food)
}

  1. random number
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package main

import (
	"fmt"
  "math/rand"
  "time"
)

func main() {
  // Add your code below:
  rand.Seed(time.Now().UnixNano())
  
  amountLeft := rand.Intn(10000)
  
  fmt.Println("amountLeft is: ", amountLeft)
  
	if amountLeft > 5000 {
		fmt.Println("What should I spend this on?")
  } else {
    fmt.Println("Where did all my money go?")
  }
}

// amountLeft is:  7298
// What should I spend this on?

  1. address use &
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package main

import "fmt"

func main() {
	treasure := "The friends we make along the way."
	
    fmt.Println(&treasure)

    // 0xc0000101e0
}

  1. Pointers are variables that specifically store addresses.
    var pointerForInt *int
    pointerForInt will store the address of a variable that has an int data type.
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lyrics := "Moments so dear" 
pointerForStr := &lyrics

*pointerForStr = "Journeys to plan" 

fmt.Println(lyrics) // Prints: Journeys to plan
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func addHundred(num int) {
  num += 100
}

func main() {
  x := 1
  addHundred(x)
  fmt.Println(x) // Prints 1
}
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func addHundred (numPtr *int) {
  *numPtr += 100
}

func main() {
  x := 1
  addHundred(&x)
  fmt.Println(x) // Prints 101
}