iOS Swift Error: 'T' Is Not Convertible to 'Mirrordisposition'

iOS Swift Error: 'T' is not convertible to 'MirrorDisposition'

You are getting an error because the compiler can't guarantee that the element stored in your array can be compared with ==. You have to ensure that it the contained type is Equatable. However, there is no way to add a method to a generic class that is more restrictive than the class itself. It is better to implement it as a function:

func removeItem<T: Equatable>(item: T, var fromArray array: [T]) -> [T] {
    for i in reverse(0 ..< array.count) {
        if array[i] == item {
            array.removeAtIndex(i)
        }
    }
    return array
}

Or you could add it as a more generic extension:

extension Array {
    mutating func removeObjectsPassingTest(test: (object: T) -> Bool) {
        for var i : Int = self.count - 1; i >= 0; --i {
            if test(object: self[i]) {
                self.removeAtIndex(i)
            }
        }
    }
}

Then you can do this:

var list: [Int] = [1,2,3,2,1]
list.removeObjectsPassingTest({$0 == 2})

float is not convertible to 'MirrorDisposition' Swift What is mirrordisposition?

MirrorDisposition is one of the types you can get from a Mirror of a value (using reflect function). They are made for the IDE to enable displaying the values.

/// How children of this value should be presented in the IDE.
enum MirrorDisposition {
    case Struct
    case Class
    case Enum
    case Tuple
    case Aggregate
    case IndexContainer
    case KeyContainer
    case MembershipContainer
    case Container
    case Optional
    case ObjCObject
}

The error message means that the compiler didn't find an == operator to compare a Float with an Int. However, it probably found an == operator for MirrorDisposition and Int, so it is trying to convert Float to MirrorDisposition but it obviously can't, so you get an error message.

(by the way, the type error you get is random, depending on the operator the compiler tries to use. I am getting Float is not convertible to Selector).

The error message is a bug, there should be a message saying Could not find == operator for Float and Int.

The obvious fix to check value equality is using a cast:

if intValue == Int(floatValue)  {

There is no reason to compare types this way because in Swift, types are checked by the compiler. There should never be a reason to check the type explicitly (speaking about value types, not object types, of course).

Can't perform an IF statement on a UITableViewCell in Swift? Error: is not convertible to MirrorDisposition

cell is not an Optional therefore it will never be nil. Try this instead, declaring cell as an NDTableViewCell? and then unwrapping it before the return.

var cell:NDTableViewCell? = tableView.dequeueReusableCellWithIdentifier(NDTableViewCell.identifier) as? NDTableViewCell

if (cell == nil) { // Error happens here!
   cell = NDTableViewCell.loadFromNib()
}

return cell!

Also, see this answer for more details about the failed comparison: float is not convertible to 'MirrorDisposition' Swift What is mirrordisposition?

NSError' is not convertible to '@lvalue inout $T9' in Swift

You are reusing the error variable passed in to the block - you simply have to define a local optional variable and pass its reference to JSONObjectWithData

var myError: NSError?
self.data = NSJSONSerialization.JSONObjectWithData(response, options:NSJSONReadingOptions.MutableLeaves, error: &myError)

That happens because JSONObjectWithData needs a reference to a variable of NSError type. The one passed to the block is immutable - it points to an instance of NSError, but cannot be reassigned to point to another instance, or set to nil in case of no error.

Swift String is not convertible to 'MirorDisposition' error

You probably have to check whether array[0] doesn't contain the "1" string instead of an integer value

Error: Int is not convertible to NSRange

NSRange is a struct with members location and length, not an Int

use the initializer

var range: NSRange = NSRange(location:0, length:0)

or the convenience function

var range: NSRange = NSMakeRange(0, 0)

CGFloat is not convertible to Int when trying to calculate an expression

You have already explained and solved the matter perfectly. It's simply a matter of you accepting your own excellent explanation:

It works perfectly fine if ... I just give it a literal value ... But when I go with any variable or constant or expression containing one, it displays an error "CGFloat is not convertible to Int".

Correct. Numeric literals can be automatically coerced to another type, such as CGFloat. But variables cannot; you must coerce them, explicitly. To do so, initialize a new number, of the correct type, based on the old number.

So, this works automagically:

let f1 : CGFloat = 1.0
let f2 = f1 + 1

But here, you have to coerce:

let f1 : CGFloat = 1.0
let f2 = 1
let f3 = f1 + CGFloat(f2)

It's a pain, but it keeps you honest, I guess. Personally I agree with your frustration, as my discussion here will show: Swift numerics and CGFloat (CGPoint, CGRect, etc.) It is hard to believe that a modern language is expected to work with such clumsy numeric handling, especially when we are forced against our will to bang into the Core Graphics CGFloat type so frequently in real-life Cocoa programming. But that, it seems, is the deal. I keep hoping that Swift will change in this regard, but it hasn't happened so far. And there is a legitimate counterargument that implicit coercion, which is what we were doing in Objective-C, is dangerous (and indeed, things like the coming of 64-bit have already exposed the danger).

Enumerating with a for-in loop

while summaryValues[dayIndex]==nil{ // ERROR

summaryValues is an array and array[i] won't return nil. It will either return the element or it will crash if your index is out of range. First, the compiler is probably confused from comparing Int and nil. Second, trying to access summaryValues[dayIndex] here will crash, because at the time you are checking it the array is empty and the index does not exist.

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