无法将字符串解组为struct类型的Go值

Question

I run below javascript code.

return $.ajax({
                    url: "/loyalty/api/rule/new",
                    type: "POST",
                    contentType: "application/json",
                    data: JSON.stringify({'rule':$('form').serializeObject(),'ruleId':ruleID(),'programId':parseInt(proID)})
 });

and I use below code to decode it.

decoder := json.NewDecoder(r.Body)
    var rules models.NewRule
    err := decoder.Decode(&rules)

but then it gives below error message.

level=error msg="json: cannot unmarshal string into Go value of type models.NewRule" api="/rule/new" code=400 tenantid=7 username=admin 

can you help me to fix this?

my NewRule struct

type NewRule struct {
    TenantID  int                `db:"tenantId"json:"tenantId"`
    ProgramID commons.NullInt64  `db:"programId"json:"programId"`
    RuleID    commons.NullInt64  `db:"ruleId"json:"ruleId"`
    Rule      commons.NullString `db:"rule"json:"rule"`
}

func (p NewRule) String() string {
    b, _ := json.Marshal(p)
    return string(b)
}

Answer 1

I think you're misunderstanding how serializeObject works in JavaScript. From the fine manual:

.serializeObject — serializes the selected form into a JavaScript object

$('form#contact').serializeObject();
//=> {user: {email: "[e-mail]", pets: ["cat", "dog"]}}

.serializeJSON — serializes the selected form into JSON

$('form#contact').serializeJSON();
//=> '{"user":{"email":"[e-mail]","pets":["cat","dog"]}}'

serializeObject gives you an object so this:

{'rule': $('form').serializeObject(), 'ruleId': ruleID(), 'programId': parseInt(proID)}

will give you something like this JavaScript:

{
    rule: { /* some JavaScript object goes here */ },
    ruleId: 6,
    programId: 11
}

So the "rule" key in the JSON will have a whole object (not a string) as its value and decoder.Decode correctly refuses to unpack an object into a string.

If you want the rule to be a string of JSON encoded data when you unpack it then you want JSON inside your JSON:

data: JSON.stringify({
    'rule': $('form').serializeJSON(), // <---- serialize the form to JSON, not an object
    'ruleId': ruleID(),
    'programId': parseInt(proID)
})

Then what you're doing should work and you'll end up with JSON encoded data in rules.Rule in Go.