Moya: nil value in JSON POST body

[philipengberg]

Version 8.0.2

I feel kinda stupid to be asking the seemingly simple question, but I simply can't figure it out.

I need to post some JSON to an API endpoint, where some values need to be nil. Here's an example:

{
    "key1": "someString",
    "key2": null
}

However, the parameters property of the TargetType protocol only accepts [String, Any]? and not [String, Any?]?, so how do you achieve this?

[vzsg]

Use NSNull() to fill that entry in your dictionary.

[philipengberg]

Thanks @vzsg. But I'm curious as to why you need to use some old NSObject subclass in a Swift dictionary, when we have optionals?

Also, what is the easiest way to unwrap the optional values when constructing the parameters dictionary then? Let's say I have an object

struct LineupPlayer {
    let id: Int
    let user : User?
}

doing the following

extension LineupPlayer : ParameterRepresentation {
    var representation: [String : Any] {
        return ["id": id, "user": user?.representation ?? NSNull()]
    }

results in a compile error Generic parameter 'T' could not be inferred, since the nil-coalescing operator tries to operate on two different types.

How would you recommend to do this?

[jessearmand]

To provide a default value of an optional of [String: Any], you could use an empty dictionary [:] instead of NSNull.

On 12 Mar 2017, 4:27 PM +0800, Philip Engberg [e-mail], wrote:
>

Thanks @vzsg (https://github.com/vzsg). But I'm curious as to why you need to use some old NSObject subclass in a Swift dictionary, when we have optionals?

Also, what is the easiest way of constructing the parameters dictionary then? Let's say I have an object

struct LineupPlayer { let id: Int let user : _User? }

doing the following

extension LineupPlayer : ParameterRepresentation { var representation: [String : Any] { return ["id": id, "user": user?.representation ?? NSNull()] }

results in a compile error Generic parameter 'T' could not be inferred, since the nil-coalescing operator tries to operate on two different types.

How would you recommend to do this?

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[philipengberg]

Doing

extension LineupPlayer : ParameterRepresentation {
    var representation: [String : Any] {
        return ["id": id, "user": (user?.representation as? Any`) ?? NSNull()]
    }

compiles, but now I get this error 🙄 I'm so confused!

[jessearmand]

Why don't you do it as the following? Also, what is the type of representation? Is it the same as LineupPlayer representation?

/// What is the expected type of user?.representation

extension LineupPlayer : ParameterRepresentation {
    var representation: [String : Any] {
        return ["id": id, "user": user?.representation as? [String: Any] ?? [:]]
    }
}

[philipengberg]

It's just a protocol

protocol ParameterRepresentation {
    var representation : [String : Any] { get }
}

Because the API only accepts null, not { }, when there is no value @jessearmand.

[jessearmand]

Alright, understood. It compiles, but there's an error? or a warning?

If it's a warning I don't think that is an issue since that is what you're doing, coercing [String: Any] to Any and using NSNull as a default, which is a different type from [String: Any].

[philipengberg]

I got it working now. Thanks everyone 🙏

[sunshinejr]

Great! Could you post your fix to the problem here as well, @philipengberg? Might be helpful for other people in the future.

[levibostian]

Leaving this here as reference in case others would find it useful. I was able to use the comments on this issue to help me with my problem of sending the value nil as a parameter value in my network request body.

Moya version: 12.0.1
Swift version: 4.2

struct Contact {
    let name: String 
    let email: String?
} 

/**
 API requires body of JSON to be in format: 
  {
    "contacts": [
        {"name": "Name Here", "email": nil},
        {"name": "Other Name", "email": "[email protected]"}
    ]
  }

It requires nil to be used if the email field does not exist locally.
*/

let contacts: [Contact] = getContacts()

var contactsRequest = [
    [String: Any]
]()
for contact in contacts {
    contactsRequest.append([
        "name": contact.name,
        "email": (contact.email ?? NSNull()) as Any
    ])
}

let parameters = ["contacts": contactsRequest]

// Use `parameters` in `TargetType` for Moya request body. 

After checking the my Moya network log, the request sent to the API is indeed:

{
    "contacts": [
        {"name": "Name Here", "email": nil},
        {"name": "Other Name", "email": "[email protected]"}
    ]
}

Where nil is sent in the request for the "email" parameter.