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Golang - Asterisk and Ampersand Cheatsheet
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| /* | |
| ******************************************************************************** | |
| Golang - Asterisk and Ampersand Cheatsheet | |
| ******************************************************************************** | |
| Also available at: https://play.golang.org/p/cLHwQ1cSqKY | |
| Allowed: | |
| -------- | |
| p := Person{"Steve", 28} stores the value | |
| p := &Person{"Steve", 28} stores the pointer address (reference) | |
| PrintPerson(p) passes either the value or pointer address (reference) | |
| PrintPerson(*p) passes the value | |
| PrintPerson(&p) passes the pointer address (reference) | |
| func PrintPerson(p Person) ONLY receives the value | |
| func PrintPerson(p *Person) ONLY receives the pointer address (reference) | |
| Not Allowed: | |
| -------- | |
| p := *Person{"Steve", 28} illegal | |
| func PrintPerson(p &Person) illegal | |
| */ | |
| package main | |
| import ( | |
| "fmt" | |
| ) | |
| type Person struct { | |
| Name string | |
| Age int | |
| } | |
| // This only works with *Person, does not work with Person | |
| // Only works with Test 2 and Test 3 | |
| func (p *Person) String() string { | |
| return fmt.Sprintf("%s is %d", p.Name, p.Age) | |
| } | |
| // This works with both *Person and Person, BUT you can't modiy the value and | |
| // it takes up more space | |
| // Works with Test 1, Test 2, Test 3, and Test 4 | |
| /*func (p Person) String() string { | |
| return fmt.Sprintf("%s is %d", p.Name, p.Age) | |
| }*/ | |
| // ***************************************************************************** | |
| // Test 1 - Pass by Value | |
| // ***************************************************************************** | |
| func test1() { | |
| fmt.Println("Test 1 - Pass by Value") | |
| p := Person{"Steve", 28} | |
| printPerson1(p) | |
| updatePerson1(p) | |
| printPerson1(p) | |
| } | |
| func updatePerson1(p Person) { | |
| p.Age = 32 | |
| printPerson1(p) | |
| } | |
| func printPerson1(p Person) { | |
| fmt.Printf("String: %v | Name: %v | Age: %d\n", | |
| p, | |
| p.Name, | |
| p.Age) | |
| } | |
| // ***************************************************************************** | |
| // Test 2 - Pass by Reference | |
| // ***************************************************************************** | |
| func test2() { | |
| fmt.Println("Test 2 - Pass by Reference") | |
| p := &Person{"Steve", 28} | |
| printPerson2(p) | |
| updatePerson2(p) | |
| printPerson2(p) | |
| } | |
| func updatePerson2(p *Person) { | |
| p.Age = 32 | |
| printPerson2(p) | |
| } | |
| func printPerson2(p *Person) { | |
| fmt.Printf("String: %v | Name: %v | Age: %d\n", | |
| p, | |
| p.Name, | |
| p.Age) | |
| } | |
| // ***************************************************************************** | |
| // Test 3 - Pass by Reference (requires more typing) | |
| // ***************************************************************************** | |
| func test3() { | |
| fmt.Println("Test 3 - Pass by Reference (requires more typing)") | |
| p := Person{"Steve", 28} | |
| printPerson3(&p) | |
| updatePerson3(&p) | |
| printPerson3(&p) | |
| } | |
| func updatePerson3(p *Person) { | |
| p.Age = 32 | |
| printPerson3(p) | |
| } | |
| func printPerson3(p *Person) { | |
| fmt.Printf("String: %v | Name: %v | Age: %d\n", | |
| p, | |
| p.Name, | |
| p.Age) | |
| } | |
| // ***************************************************************************** | |
| // Test 4 - Pass by Value (requires more typing) | |
| // ***************************************************************************** | |
| func test4() { | |
| fmt.Println("Test 4 - Pass by Value (requires more typing)") | |
| p := &Person{"Steve", 28} | |
| printPerson4(*p) | |
| updatePerson4(*p) | |
| printPerson4(*p) | |
| } | |
| func updatePerson4(p Person) { | |
| p.Age = 32 | |
| printPerson4(p) | |
| } | |
| func printPerson4(p Person) { | |
| fmt.Printf("String: %v | Name: %v | Age: %d\n", | |
| p, | |
| p.Name, | |
| p.Age) | |
| } | |
| // ***************************************************************************** | |
| // Main | |
| // ***************************************************************************** | |
| /* | |
| Outputs: | |
| String: {Steve 28} | Name: Steve | Age: 28 | |
| String: {Steve 32} | Name: Steve | Age: 32 | |
| String: {Steve 28} | Name: Steve | Age: 28 | |
| String: Steve is 28 | Name: Steve | Age: 28 | |
| String: Steve is 32 | Name: Steve | Age: 32 | |
| String: Steve is 32 | Name: Steve | Age: 32 | |
| String: Steve is 28 | Name: Steve | Age: 28 | |
| String: Steve is 32 | Name: Steve | Age: 32 | |
| String: Steve is 32 | Name: Steve | Age: 32 | |
| String: {Steve 28} | Name: Steve | Age: 28 | |
| String: {Steve 32} | Name: Steve | Age: 32 | |
| String: {Steve 28} | Name: Steve | Age: 28 | |
| */ | |
| func main() { | |
| test1() | |
| test2() | |
| test3() | |
| test4() | |
| } |
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