go get -u github.com/golang-infrastructure/go-pointer
In golang, the primitive type has no wrapping type, so the primitive type can't distinguish between nil and zero, so many libraries tend to use Pointers to primitive variables to distinguish between zero and not passed.
For a specific example, when no Pointers are used, there is a configuration item when executing a task:
package main
type Config struct {
Foo int
}When Foo is 0, we do not know whether we have passed zero or no value, because some libraries prefer to use pointer types in this case:
package main
type Config struct {
Foo *int
}However, sometimes this value is passed in as a literal constant, such as the paging size when querying a database. In this case, getting a pointer type can be a bit of a hassle:
package main
func main() {
foo := 10
config := &Config{
Foo: &foo,
}
callSomeFunction(config)
}If using this library:
package main
func main() {
config := &Config{
Foo: pointer.ToPointer(10)
}
callSomeFunction(config)
}Diff:
package main
func main() {
- foo := 10
config := &Config{
- Foo: &foo,
+ Foo: pointer.ToPointer(10)
}
callSomeFunction(config)
}The above scenario is just an example of a problem that this module is designed to solve.
Generics are already supported:
package main
import (
"fmt"
pointer "github.com/golang-infrastructure/go-reflect-utils"
)
func main() {
// Returns a pointer to false
falsePointer := pointer.FalsePointer()
fmt.Println(fmt.Sprintf("%T %v", falsePointer, *falsePointer)) // Output: *bool false
// Returns a pointer to true
truePointer := pointer.TruePointer()
fmt.Println(fmt.Sprintf("%T %v", truePointer, *truePointer)) // Output: *bool true
// Returns a pointer to the corresponding type
v1 := 1
toPointer := pointer.ToPointer(v1)
fmt.Println(fmt.Sprintf("%T %v", toPointer, *toPointer)) // Output: *int 1
// Returns a pointer to the corresponding type, but checks the value and returns nil if the value is zero of the corresponding type
v1 = 0
orNil := pointer.ToPointerOrNil(v1)
fmt.Println(orNil) // Output: nil
// Reads a value from a pointer, and returns a zero value of the corresponding type if it is a nil pointer
v2 := 1
v3 := &v2
fromPointer := pointer.FromPointer(v3)
fmt.Println(fromPointer) // Output: 1
// Reads the value from a pointer, and returns the given default value if it is a nil pointer
v2 = 0
orDefault := pointer.FromPointerOrDefault(v3, 1)
fmt.Println(orDefault) // Output: 0
// return time.Now() pointer
nowPointer := pointer.Now()
fmt.Println(nowPointer) // Output: 2023-05-30 11:46:20.3695476 +0800 CST m=+0.003922101
}