Last time I found out I didn't have to check if variable is nil
to make singleton service but I can use sync.Once
to achieve the same result, example below:
// instead of
var instance Instance
func NewInstance() {
if instance == nil {
instance = Instance{}
}
return instance
}
// can do this
var (
once sync.Once
instance Instance
)
func NewInstance() {
once.Do(func() {
instance = Instance{}
})
return instance
}
My question is:
Can I use sync
package to break chaining rules and return error?
Desired result:
var (
breakChain sync.SomethingToBreakChain
err error
)
type s struct {}
func (s *s) F1() s {
err = service1.DoSomething()
// sync do something
return s
}
func (s *s) F2() s {
err = service2.DoSomething()
// sync do something
return s
}
func (s *s) F3() s {
err = service3.DoSomething()
// sync do something
return s
}
func (s *s) GetError() {
return err
}
func New() {
s := s{}
s.F1(). // if error save to `err` variable and break chain here prevent `F2` and `F3` to execute
F2(). // if error save to `err` variable and break chain here prevent `F3` to execute
F3() // if error save to `err` to return
err := s.GetError()
// do something with `err`
}
CodePudding user response:
If you want to implement a chain like that, you might consider saving the error in the receiver itself and checking in every action:
type s struct {
e error
}
func (s *s) F1() *s {
if s.e!=nil {
return s
}
// Do things
if err:=doThings(); err!=nil {
s.e=err
}
return s
}
...
Otherwise, there are no mechanisms to prevent calling other methods in the chain.