Type of expression is ambiguous without more context Swift

Question

I am getting a  Type of expression is ambiguous without more context   on this part of code from a project I am trying to upgrade to latest Swift version  I can t seem to figure it out  I tried different things but can t get it to work   The problem is on the syntax of this line   let imageToDeleteParameters    imagesToDelete map     id    0 id   url    0 url absoluteString    destroy   true      Full code   extension TutorialCreationRequest  WebserviceParametrable       func toParameters   - gt   String  AnyObject            let imageParameters   images map     url    0            let imageToDeleteParameters    imagesToDelete map     id    0 id   url    0 url absoluteString    destroy   true            return                title   title               is draft   isDraft               difficulty   difficulty               duration   duration               cost   cost               user id   userId               description   description               to sell   toSell               images    imageParameters  imageToDeleteParameters  flatMap    0

User · Answer

In my case it happened with NSFetchedResultsController and the reason was that I defined the NSFetchedResultsController for a different model than I created the request for the initialization (RemotePlaylist vs. Playlist):

  var fetchedPlaylistsController:NSFetchedResultsController<RemotePlaylist>!

but initiated it with a request for another Playlist:

let request = Playlist.createFetchRequest()
fetchedPlaylistsController = NSFetchedResultsController(fetchRequest: request, ...

User · Answer

You have two     before the    let imageToDeleteParameters   imagesToDelete map     id    0 id   url    0 url absoluteString    destroy   true

User · Answer

This happens when you have a function with wrong argument names   Example   functionWithArguments argumentNameWrong    argumentName2      and You declared your function as   functionWithArguments argumentName1    argumentName2        This usually happens when you changed the name of a Variable  Make sure you refactor when you do that

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In my case  this error message shown when I don t added optional property to constructor   struct Event  Identifiable  Codable        var id  String     var summary  String     var description  String         also has other props         init id  String  summary  String  description  String            self id   id         self summary   summary         self description   description             skip pass description    It show message  Type of expression is ambiguous without more context  Event      id   1       summary   summary         pass description explicity pass nil to description Event      id   1       summary   summary       description  nil      but it looks always not occured   I test in my playground this code  it show warning about more concrete  var str    Hello  playground  struct User       var id  String     var name  String      init id  String  name  String             self id   id         self name   name          User id   hoge      Missing argument for parameter  name  in call

User · Answer

For me the case was Type inference I have changed the function parameters from int To float but did not update the calling code  and the compiler did not warn me on wrong type passed to the function Before func myFunc param Int  parma2 Int      After func myFunc param Float  parma2 Float      Calling code with error var param1 Int16   1 var param2 Int16   2 myFunc param param1  parma2 param2    error here  Type of expression is ambiguous without more context  To fix  var param1 Float   1 0f var param2 Float   2 0f myFunc param param1  parma2 param2    ok

User · Answer

Explicitly declaring the inputs for that mapping function should do the trick   let imageToDeleteParameters    imagesToDelete map        whatever   WhateverClass  - gt  Dictionary lt String  Any gt  in       id   whatever id   url   whatever url absoluteString    destroy   true      Substitute the real class of   0  for  WhateverClass  in that code snippet  and it should work

User · Answer

The compiler can t figure out what type to make the Dictionary  because it s not homogenous  You have values of different types  The only way to get around this is to make it a  String  Any   which will make everything clunky as all hell   return        title   title       is draft   isDraft       difficulty   difficulty       duration   duration       cost   cost       user id   userId       description   description       to sell   toSell       images    imageParameters  imageToDeleteParameters  flatMap    0     as  String  Any    This is a job for a struct  It ll vastly simplify working with this data structure

User · Answer

This can happen if any part of your highlighted method or property is attempting to access a property or method with the incorrect type  Here is a troubleshooting checklist   Make sure the type of arguments match in the call site and implementation  Make sure the argument names match in the call site and implementation  Make sure the method name matches in the call site and implementation  Make sure the returned value of a property or method matches in the usage and implementation  ie  enumerated    Make sure you don t have a duplicated method with potentially ambiguous types such as with protocols or generics  Make sure the compiler can infer the correct type when using type inference   A Strategy  Try breaking apart your method into a greater number of simpler method implementations   For example  lets say you are running compactMap on an array of custom Types   In the closure you are passing to the compactMap method  you initialize and return another custom struct   When you get this error  it is difficult to tell which part of your code is offending   For debugging purposes  you can use a for loop instead of compactMap  instead of passing the arguments  directly  you can assign them to constants in the for loop   By this point  you may come to a realization  such as   instead of the property you thought you wanted to assign actually had a property on it that had the actual value you wanted to pass

User · Answer

This might not be very applicable to others  but my problem was that the changes I made was NOT saved yet  Press CMD   S and save your work before building on top of it

User · Answer

Not an answer to this question  but as I came here looking for the error others might find this also useful   For me  I got this Swift error when I tried to use the for  index  object  loop on an array without adding the  enumerated   part

User · Answer

I had this message when the type of a function parameter didn t fit  In my case it was a String instead of an URL

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I got this error when I put a space before a comma in the parameters when calling a function   eg  I used   myfunction parameter1  parameter1   parameter2  parameter2    Whereas it should have been   myfunction parameter1  parameter1  parameter2  parameter2    Deleting the space got rid of the error message

User · Answer

As theEye s answer it is not an answer to this question  but as I also came here looking for the error im posting my case as others might find this also useful  I got this error message when I was by error trying to calculate a value of two different types  In my case I was trying to divide a CGFloat by a Double

[swift] Type of expression is ambiguous without more context Swift

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