Can't make multiple FBSDKGraphRequests - ios

Question

I'm trying to read the posts from a Facebook page using the following code:
class FacebookGraphAPI {
class func getPosts(fromPageWithID pageId: String, parameters: [String: AnyObject]?, completion: #escaping ([FacebookPost]?, Error?) -> Void) {
self.getAccessToken { (accessToken, error) in
if error != nil {
completion(nil, error)
return
}
let params = ["access_token": accessToken, "fields": "created_time,message,story"]
if let request = FBSDKGraphRequest(graphPath: "\(pageId)/posts", parameters: params) {
request.start { (connection, result, error) in
if error != nil {
completion(nil, error)
return
}
guard let resultDict = result as? [String: AnyObject],
let data = resultDict["data"] as? NSArray
else {
completion(nil, nil)
return
}
var posts = [FacebookPost]()
for item in data {
posts.append(FacebookPost(dict: item as! NSDictionary))
}
completion(posts, nil)
}
}
completion(nil, nil)
}
}
class func getAccessToken(completion: #escaping (String?, Error?) -> Void) {
let clientId = Bundle.main.object(forInfoDictionaryKey: "FacebookAppID") as! String
let clientSecret = Bundle.main.object(forInfoDictionaryKey: "FacebookAppSecret") as! String
let params = ["client_id": clientId, "client_secret": clientSecret, "grant_type": "client_credentials", "fields": "access_token"]
if let request = FBSDKGraphRequest(graphPath: "oauth/access_token", parameters: params) {
request.start(completionHandler: { (connection, result, error) in
if error != nil {
completion(nil, error)
return
}
guard let resultDict = result as? [String: AnyObject] else {
completion(nil, nil)
return
}
let accessToken = resultDict["access_token"] as! String
completion(accessToken, nil)
})
}
}
}
Which I then call using e.g. the following:
FacebookGraphAPI.getPosts(fromPageWithID: "{page-id}", parameters: ["limit": 5 as AnyObject]) { (posts, error) in
guard error == nil else { return }
...
}
The error I'm getting is: -[_SwiftValue length]: unrecognized selector sent to instance on the second FBSDKGraphRequest start.
I tried removing the first FBSDKGraphRequest and then I at least get a response in the completionHandler. It almost seams as if I can't make more than one FBSDKGraphRequest.
Any help is greatly appreciated.
Thanks in advance!

Answer 1

I finally managed to find the issue, when thinking about the error and remembering that the FBSDKCoreKit framework was written in Objective-C.
All I needed to do was cast accessToken inside the parameters array to an NSString.
I changed the following:
let params = ["access_token": accessToken, "fields": "created_time,message,story"]
To:
let params = ["access_token": accessToken! as NSString, "fields": "created_time,message,story"]