Type of expression is ambiguous without more context Swift

Question

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.

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.
• the argument names match in the call site and implementation.
• the method name matches in the call site and implementation.
• the returned value of a property or method matches in the usage and implementation (ie: enumerated())
• you don't have a duplicated method with potentially ambiguous types such as with protocols or generics.
• 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 in 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.

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 ...

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.

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.