how to distinguish between missing attributes and attributes with default values?
Use pointers!
Imagine the following:
type Person struct { Name *string Age int }
then try to unmarshal this: { "Age": 30 }
{ "Age": 30 }
You will get this:
fmt.Printf("%#v\n", p) > main.Person{Name:(*string)(nil), Age:30}
if a key is missing, it's a simple nil check away.
Another nice technique I like to use is as follows:
Declare an ok interface:
ok
type ok interface { OK() error }
Implement it on your type:
func (p *Person) OK() error { if p.Name == nil { return errors.New("missing field: name") } return nil }
Then simply:
p.OK() > 2009/11/10 23:00:00 missing field: name
You can see the full example in the go playground:
play.golang.org/p/P_88niVqOke
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Use pointers!
Imagine the following:
then try to unmarshal this:
{ "Age": 30 }You will get this:
if a key is missing, it's a simple nil check away.
Another nice technique I like to use is as follows:
Declare an
okinterface:Implement it on your type:
Then simply:
You can see the full example in the go playground:
play.golang.org/p/P_88niVqOke