Expression type is ambiguous without additional Swift context

Question

I get the “ Type of expression ambiguous without context ” in this part of the code from the project that I am trying to upgrade to the latest version of Swift. I don't seem to understand. I tried different things, but I can not get it to work.

The problem is 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() -> [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 } ] } } 

Answer 1

Not the answer to this question, but since I came here looking for an error, others may find this also useful:

For me, I got this Swift error when I tried to use a for (index, object) loop for (index, object) array without adding the .enumerated() ...

Answer 2

The compiler cannot figure out what type of dictionary is because it is not homogeneous. You have different types of values. The only way around this is to make it [String: Any] , which will make everything awkward, like 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 the structure. This will greatly simplify the work with this data structure.

Answer 3

This happens when you have a function with invalid argument names.

Example:

 functionWithArguments(argumentNameWrong: , argumentName2: ) 

and you declared your function as:

 functionWithArguments(argumentName1: , argumentName2: ){} 

This usually happens when you change the name of a variable. Make sure you refactor when you do this.

Answer 4

An explicit input declaration for this display function should do the trick:

 let imageToDeleteParameters = imagesToDelete.map { (whatever : WhateverClass) -> Dictionary<String, Any> in ["id": whatever.id, "url": whatever.url.absoluteString, "_destroy": true] } 

Substitute the real class "$ 0" for "WhateverClass" in this piece of code, and it should work.

Answer 5

I got this error when I put a space before the comma in the parameters when calling the function.

For example, I used:

 myfunction(parameter1: parameter1 , parameter2: parameter2) 

Whereas it should have been:

 myfunction(parameter1: parameter1, parameter2: parameter2) 

Removing the space eliminated the error message

Answer 6

I had this message when the function parameter type did not fit. In my case, it was a string instead of a URL.