gh-mirrors/bootdotdev-fcc-learn-golang-assets
1
0
Fork 0
mirror of https://github.com/bootdotdev/fcc-learn-golang-assets.git synced 2025-12-18 03:01:16 +00:00
Code Issues Packages Projects Releases Wiki Activity

first

Browse Source
This commit is contained in:
wagslane
2023-05-01 15:25:27 -06:00
parent f8912668b8
commit 9be3074de6
868 changed files with 58698 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

29
course/11-pointers/exercises/1-pointers_intro/code.go Normal file
View File

@@ -0,0 +1,29 @@
package main
import "fmt"
type Message struct {
Recipient string
Text string
}
// Don't touch above this line
func sendMessage(m Message) {
fmt.Printf("To: %v\n", &m.Recipient)
fmt.Printf("Message: %v\n", &m.Text)
}
// Don't touch below this line
func test(recipient string, text string) {
m := Message{Recipient: recipient, Text: text}
sendMessage(m)
fmt.Println("=====================================")
}
func main() {
test("Lane", "Textio is getting better everyday!")
test("Allan", "This pointer stuff is weird...")
test("Tiffany", "What time will you be home for dinner?")
}

29
course/11-pointers/exercises/1-pointers_intro/complete.go Normal file
View File

@@ -0,0 +1,29 @@
package main
import "fmt"
type Message struct {
Recipient string
Text string
}
// Don't touch above this line
func sendMessage(m Message) {
fmt.Printf("To: %v\n", m.Recipient)
fmt.Printf("Message: %v\n", m.Text)
}
// Don't touch below this line
func test(recipient string, text string) {
m := Message{Recipient: recipient, Text: text}
sendMessage(m)
fmt.Println("=====================================")
}
func main() {
test("Lane", "Textio is getting better everyday!")
test("Allan", "This pointer stuff is weird...")
test("Tiffany", "What time will you be home for dinner?")
}

9
course/11-pointers/exercises/1-pointers_intro/expected.txt Executable file
View File

@@ -0,0 +1,9 @@
To: Lane
Message: Textio is getting better everyday!
=====================================
To: Allan
Message: This pointer stuff is weird...
=====================================
To: Tiffany
Message: What time will you be home for dinner?
=====================================

33
course/11-pointers/exercises/1-pointers_intro/readme.md Normal file
View File

@@ -0,0 +1,33 @@
# Introduction to Pointers
As we have learned, a variable is a named location in memory that stores a value. We can manipulate the value of a variable by assigning a new value to it or by performing operations on it. When we assign a value to a variable, we are storing that value in a specific location in memory.
```go
x := 42
// "x" is the name of a location in memory. That location is storing the integer value of 42
```
## A pointer is a variable
A pointer is a variable that stores the *memory address* of another variable. This means that a pointer "points to" the *location* of where the data is stored *NOT* the actual data itself.
The `*` syntax defines a pointer:
```go
var p *int
```
The `&` operator generates a pointer to its operand.
```go
myString := "hello"
myStringPtr = &myString
```
## Why are pointers useful?
Pointers allow us to manipulate data in memory directly, without making copies or duplicating data. This can make programs more efficient and allow us to do things that would be difficult or impossible without them.
## Assignment
Fix the bug in the `sendMessage` function. It's *supposed* to print a nicely formatted message to the console containing an SMS's recipient and message body. However, it's not working as expected. Run the code and see what happens, then fix the bug.

35
course/11-pointers/exercises/2-pointers_practice/code.go Normal file
View File

@@ -0,0 +1,35 @@
package main
import (
"fmt"
)
func removeProfanity(message *string) {
// ?
}
// don't touch below this line
func test(messages []string) {
for _, message := range messages {
removeProfanity(&message)
fmt.Println(message)
}
}
func main() {
messages1 := []string{
"well shoot, this is awful",
"dang robots",
"dang them to heck",
}
messages2 := []string{
"well shoot",
"Allan is going straight to heck",
"dang... that's a tough break",
}
test(messages1)
test(messages2)
}

40
course/11-pointers/exercises/2-pointers_practice/complete.go Normal file
View File

@@ -0,0 +1,40 @@
package main
import (
"fmt"
"strings"
)
func removeProfanity(message *string) {
messageVal := *message
messageVal = strings.ReplaceAll(messageVal, "dang", "****")
messageVal = strings.ReplaceAll(messageVal, "shoot", "*****")
messageVal = strings.ReplaceAll(messageVal, "heck", "****")
*message = messageVal
}
// don't touch below this line
func test(messages []string) {
for _, message := range messages {
removeProfanity(&message)
fmt.Println(message)
}
}
func main() {
messages1 := []string{
"well shoot, this is awful",
"dang robots",
"dang them to heck",
}
messages2 := []string{
"well shoot",
"Allan is going straight to heck",
"dang... that's a tough break",
}
test(messages1)
test(messages2)
}

6
course/11-pointers/exercises/2-pointers_practice/expected.txt Normal file
View File

@@ -0,0 +1,6 @@
well *****, this is awful
**** robots
**** them to ****
well *****
Allan is going straight to ****
****... that's a tough break

45
course/11-pointers/exercises/2-pointers_practice/readme.md Normal file
View File

@@ -0,0 +1,45 @@
# Pointers
Pointers hold the memory address of a value.
The `*` syntax defines a pointer:
```go
var p *int
```
A pointer's zero value is `nil`
The & operator generates a pointer to its operand.
```go
myString := "hello"
myStringPtr = &myString
```
The * dereferences a pointer to gain access to the value
```go
fmt.Println(*myStringPtr) // read myString through the pointer
*myStringPtr = "world" // set myString through the pointer
```
Unlike C, Go has no [pointer arithmetic](https://www.tutorialspoint.com/cprogramming/c_pointer_arithmetic.htm)
## Just because you can doesn't mean you should
We're doing this exercise to understand that pointers **can** be used in this way. That said, pointers can be *very* dangerous. It's generally a better idea to have your functions accept non-pointers and return new values rather than mutating pointer inputs.
## Assignment
Complete the `removeProfanity` function.
It should use the [strings.ReplaceAll](https://pkg.go.dev/strings#ReplaceAll) function to replace all instances of the following words in the input `message` with asterisks.
* "dang" -> "****"
* "shoot" -> "*****"
* "heck" -> "****"
It should *mutate* the value in the pointer and return nothing.
Do *not* alter the function signature.

9
course/11-pointers/exercises/3-pointers_quiz/multiple_choice.json Normal file
View File

@@ -0,0 +1,9 @@
{
"question": "What is the value of *y after the code on the left executes?",
"answers": [
"100",
"a memory address pointing to x",
"nil",
"50"
]
}

13
course/11-pointers/exercises/3-pointers_quiz/readme.md Normal file
View File

@@ -0,0 +1,13 @@
# Pointers Quiz
```go
package main
import "fmt"
func main() {
var x int = 50
var y *int = &x
*y = 100
}
```

9
course/11-pointers/exercises/3b-pointers_quiz/multiple_choice.json Normal file
View File

@@ -0,0 +1,9 @@
{
"question": "What is the value of x after the code on the left executes?",
"answers": [
"100",
"a memory address pointing to x",
"50",
"nil"
]
}

13
course/11-pointers/exercises/3b-pointers_quiz/readme.md Normal file
View File

@@ -0,0 +1,13 @@
# Pointers Quiz
```go
package main
import "fmt"
func main() {
var x int = 50
var y *int = &x
*y = 100
}
```

51
course/11-pointers/exercises/4-nil_dereference/code.go Normal file
View File

@@ -0,0 +1,51 @@
package main
import (
"fmt"
"strings"
)
func removeProfanity(message *string) {
// ?
messageVal := *message
messageVal = strings.ReplaceAll(messageVal, "dang", "****")
messageVal = strings.ReplaceAll(messageVal, "shoot", "*****")
messageVal = strings.ReplaceAll(messageVal, "heck", "****")
*message = messageVal
}
// don't touch below this line
func test(messages []string) {
for _, message := range messages {
if message == "" {
removeProfanity(nil)
fmt.Println("nil message detected")
} else {
removeProfanity(&message)
fmt.Println(message)
}
}
}
func main() {
messages := []string{
"well shoot, this is awful",
"",
"dang robots",
"dang them to heck",
"",
}
messages2 := []string{
"well shoot",
"",
"Allan is going straight to heck",
"dang... that's a tough break",
"",
}
test(messages)
test(messages2)
}

53
course/11-pointers/exercises/4-nil_dereference/complete.go Normal file
View File

@@ -0,0 +1,53 @@
package main
import (
"fmt"
"strings"
)
func removeProfanity(message *string) {
if message == nil {
return
}
messageVal := *message
messageVal = strings.ReplaceAll(messageVal, "dang", "****")
messageVal = strings.ReplaceAll(messageVal, "shoot", "*****")
messageVal = strings.ReplaceAll(messageVal, "heck", "****")
*message = messageVal
}
// don't touch below this line
func test(messages []string) {
for _, message := range messages {
if message == "" {
removeProfanity(nil)
fmt.Println("nil message detected")
} else {
removeProfanity(&message)
fmt.Println(message)
}
}
}
func main() {
messages := []string{
"well shoot, this is awful",
"",
"dang robots",
"dang them to heck",
"",
}
messages2 := []string{
"well shoot",
"",
"Allan is going straight to heck",
"dang... that's a tough break",
"",
}
test(messages)
test(messages2)
}

10
course/11-pointers/exercises/4-nil_dereference/expected.txt Normal file
View File

@@ -0,0 +1,10 @@
well *****, this is awful
nil message detected
**** robots
**** them to ****
nil message detected
well *****
nil message detected
Allan is going straight to ****
****... that's a tough break
nil message detected

9
course/11-pointers/exercises/4-nil_dereference/readme.md Normal file
View File

@@ -0,0 +1,9 @@
# Nil Pointers
Pointers can be very dangerous.
If a pointer points to nothing (the zero value of the pointer type) then dereferencing it will cause a runtime error (a [panic](https://gobyexample.com/panic)) that crashes the program. Generally speaking, whenever you're dealing with pointers you should check if it's `nil` before trying to dereference it.
## Assignment
Let's make our profanity checker *safe*. Update the `removeProfanity` function. If `message` is `nil`, `return` early to avoid a [panic](https://gobyexample.com/panic). After all, there are no bad words to remove.

7
course/11-pointers/exercises/5-pointer_receiver/multiple_choice.json Normal file
View File

@@ -0,0 +1,7 @@
{
"question": "Which is more widely used in Go?",
"answers": [
"Pointer receivers",
"Value receivers"
]
}

47
course/11-pointers/exercises/5-pointer_receiver/readme.md Normal file
View File

@@ -0,0 +1,47 @@
# Pointer Receivers
A receiver type on a method can be a pointer.
Methods with pointer receivers can modify the value to which the receiver points. Since methods often need to modify their receiver, pointer receivers are *more common* than value receivers.
## Pointer receiver
```go
type car struct {
color string
}
func (c *car) setColor(color string) {
c.color = color
}
func main() {
c := car{
color: "white",
}
c.setColor("blue")
fmt.Println(c.color)
// prints "blue"
}
```
## Non-pointer receiver
```go
type car struct {
color string
}
func (c car) setColor(color string) {
c.color = color
}
func main() {
c := car{
color: "white",
}
c.setColor("blue")
fmt.Println(c.color)
// prints "white"
}
```

49
course/11-pointers/exercises/6-pointer_receiver_code/code.go Normal file
View File

@@ -0,0 +1,49 @@
package main
import (
"fmt"
)
func (e email) setMessage(newMessage string) {
e.message = newMessage
}
// don't edit below this line
type email struct {
message string
fromAddress string
toAddress string
}
func test(e *email, newMessage string) {
fmt.Println("-- before --")
e.print()
fmt.Println("-- end before --")
e.setMessage("this is my second draft")
fmt.Println("-- after --")
e.print()
fmt.Println("-- end after --")
fmt.Println("==========================")
}
func (e email) print() {
fmt.Println("message:", e.message)
fmt.Println("fromAddress:", e.fromAddress)
fmt.Println("toAddress:", e.toAddress)
}
func main() {
test(&email{
message: "this is my first draft",
fromAddress: "sandra@mailio-test.com",
toAddress: "bullock@mailio-test.com",
}, "this is my second draft")
test(&email{
message: "this is my third draft",
fromAddress: "sandra@mailio-test.com",
toAddress: "bullock@mailio-test.com",
}, "this is my fourth draft")
}

49
course/11-pointers/exercises/6-pointer_receiver_code/complete.go Normal file
View File

@@ -0,0 +1,49 @@
package main
import (
"fmt"
)
func (e *email) setMessage(newMessage string) {
e.message = newMessage
}
// don't edit below this line
type email struct {
message string
fromAddress string
toAddress string
}
func test(e *email, newMessage string) {
fmt.Println("-- before --")
e.print()
fmt.Println("-- end before --")
e.setMessage("this is my second draft")
fmt.Println("-- after --")
e.print()
fmt.Println("-- end after --")
fmt.Println("==========================")
}
func (e email) print() {
fmt.Println("message:", e.message)
fmt.Println("fromAddress:", e.fromAddress)
fmt.Println("toAddress:", e.toAddress)
}
func main() {
test(&email{
message: "this is my first draft",
fromAddress: "sandra@mailio-test.com",
toAddress: "bullock@mailio-test.com",
}, "this is my second draft")
test(&email{
message: "this is my third draft",
fromAddress: "sandra@mailio-test.com",
toAddress: "bullock@mailio-test.com",
}, "this is my fourth draft")
}

22
course/11-pointers/exercises/6-pointer_receiver_code/expected.txt Normal file
View File

@@ -0,0 +1,22 @@
-- before --
message: this is my first draft
fromAddress: sandra@mailio-test.com
toAddress: bullock@mailio-test.com
-- end before --
-- after --
message: this is my second draft
fromAddress: sandra@mailio-test.com
toAddress: bullock@mailio-test.com
-- end after --
==========================
-- before --
message: this is my third draft
fromAddress: sandra@mailio-test.com
toAddress: bullock@mailio-test.com
-- end before --
-- after --
message: this is my second draft
fromAddress: sandra@mailio-test.com
toAddress: bullock@mailio-test.com
-- end after --
==========================

33
course/11-pointers/exercises/6-pointer_receiver_code/readme.md Normal file
View File

@@ -0,0 +1,33 @@
# Pointer Receiver Code
Methods with pointer receivers don't require that a pointer is used to call the method. The pointer will automatically be derived from the value.
```go
type circle struct {
x int
y int
radius int
}
func (c *circle) grow(){
c.radius *= 2
}
func main(){
c := circle{
x: 1,
y: 2,
radius: 4,
}
// notice c is not a pointer in the calling function
// but the method still gains access to a pointer to c
c.grow()
fmt.Println(c.radius)
// prints 8
}
```
## Assignment
Fix the bug in the code so that `setMessage` sets the `message` field of the given email structure, and the new value persists outside the scope of the `setMessage` method.