英文:
How to initialise a pointer member in a struct type inline?
问题
使用以下方法可以在内联方式下将指针成员初始化为非零值，而无需创建临时变量：
a := A{
B: 42,
C: new(int),
}
在上述代码中，我们使用new(int)来创建一个新的int类型的指针，并将其分配给C成员。这样，C成员就被初始化为一个指向非零值的指针。
英文:
With a type:
type A struct {
B int, C *int
}
How do I initialise a pointer member to a non-zero value inline, without creating temporaries?
a := A{
B: 42,
C: ?,
}
答案1
得分: 15
对于你给出的具体示例，如果不引入额外的语句，你的操作是有限的。
如果你想让 C 指向一个已初始化的整数变量，你需要额外的语句来定义该变量，因为你不能取一个整数字面量的地址（即 &42 会报错）。
如果你只想将 C 初始化为指向一个新的零值，那么你很幸运，可以将它设置为 new(int)。
如果你处理的是一个具有初始化语法的不同类型，你也会很幸运。例如，如果 C 是一个指向结构体的指针，你可以将它初始化为 &TheStruct{...}。
如果以上都不适用，并且你真的只是为了代码清晰性而初始化 *int 变量，那么一个辅助函数可能符合你的要求。例如：
func makeIntPointer(v int) *int {
return &v
}
英文:
For the specific example you've given you are limited in what you can do without introducing additional statements.
If you want C to point at an initialised integer variable, you will need an additional statement to define that variable since you can't take the address of an integer literal (i.e. &42 would be an error).
If you just want to initialise C as a pointer to a new zero value, you are in luck though and can set it to new(int).
If you were instead dealing with a different type that had an initialiser syntax, you would also been in luck. For example, if C was a pointer to a structure, you could initialise it to &TheStruct{...}.
If none of these are appropriate, and you are really only after code clarity for initialising *int variables, a helper function might fit your requirements. For example:
func makeIntPointer(v int) *int {
return &v
}
答案2
得分: 2
package main
import "fmt"
type A struct {
B int
C *int
}
func newint(i int) *int {
return &i
}
func main() {
c := newint(5)
a := &A{
B: 42,
C: c,
}
fmt.Printf(" %v", *a.C)
fmt.Printf(" %#v", a.C)
}
package main
import "fmt"
type A struct {
B int
C *int
}
func newint(i int) *int {
return &i
}
func main() {
c := newint(5)
a := &A{
B: 42,
C: c,
}
fmt.Printf(" %v", *a.C)
fmt.Printf(" %#v", a.C)
}
package main
import "fmt"
type A struct {
B int
C *int
}
func newint(i int) *int {
return &i
}
func main() {
c := newint(5)
a := &A{
B: 42,
C: c,
}
fmt.Printf(" %v", *a.C)
fmt.Printf(" %#v", a.C)
}
package main
import "fmt"
type A struct {
B int
C *int
}
func newint(i int) *int {
return &i
}
func main() {
c := newint(5)
a := &A{
B: 42,
C: c,
}
fmt.Printf(" %v", *a.C)
fmt.Printf(" %#v", a.C)
}
package main
import "fmt"
type A struct {
B int
C *int
}
func newint(i int) *int {
return &i
}
func main() {
c := newint(5)
a := &A{
B: 42,
C: c,
}
fmt.Printf(" %v", *a.C)
fmt.Printf(" %#v", a.C)
}
package main
import "fmt"
type A struct {
B int
C *int
}
func newint(i int) *int {
return &i
}
func main() {
c := newint(5)
a := &A{
B: 42,
C: c,
}
fmt.Printf(" %v", *a.C)
fmt.Printf(" %#v", a.C)
}
package main
import "fmt"
type A struct {
B int
C *int
}
func newint(i int) *int {
return &i
}
func main() {
c := newint(5)
a := &A{
B: 42,
C: c,
}
fmt.Printf(" %v", *a.C)
fmt.Printf(" %#v", a.C)
}
package main
import "fmt"
type A struct {
B int
C *int
}
func newint(i int) *int {
return &i
}
func main() {
c := newint(5)
a := &A{
B: 42,
C: c,
}
fmt.Printf(" %v", *a.C)
fmt.Printf(" %#v", a.C)
}
package main
import "fmt"
type A struct {
B int
C *int
}
func newint(i int) *int {
return &i
}
func main() {
c := newint(5)
a := &A{
B: 42,
C: c,
}
fmt.Printf(" %v", *a.C)
fmt.Printf(" %#v", a.C)
}
英文:
package main
import "fmt"
type A struct {
B int
C *int
}
func newint(i int) *int{
return &i
}
func main() {
c := newint(5)
a := &A{
B: 42,
C: c,
}
fmt.Printf(" %v" , *a.C)
fmt.Printf(" %#v" , a.C)
}
通过集体智慧和协作来改善编程学习和解决问题的方式。致力于成为全球开发者共同参与的知识库，让每个人都能够通过互相帮助和分享经验来进步。
评论