What Is Darwinboolean Type in Swift

What is DarwinBoolean type in Swift

Short answer:

• Bool is the native Swift type for truth values.
• DarwinBoolean is the Swift mapping of the "historic" C type Boolean.
• ObjCBool is the Swift mapping of the Objective-C type BOOL.

You would use Bool in your Swift code unless one of the other types
is required for interoperability with existing Core Foundation or
Objective-C functions.

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More about DarwinBoolean:
DarwinBoolean is defined in Swift as

/// The `Boolean` type declared in MacTypes.h and used throughout Core
/// Foundation.
///
/// The C type is a typedef for `unsigned char`.
public struct DarwinBoolean : BooleanType, BooleanLiteralConvertible {
    public init(_ value: Bool)
    /// The value of `self`, expressed as a `Bool`.
    public var boolValue: Bool { get }
    /// Create an instance initialized to `value`.
    public init(booleanLiteral value: Bool)
}

and is the Swift mapping of the "historic" C type Boolean from
MacTypes.h:

/********************************************************************************

    Boolean types and values

        Boolean         Mac OS historic type, sizeof(Boolean)==1
        bool            Defined in stdbool.h, ISO C/C++ standard type
        false           Now defined in stdbool.h
        true            Now defined in stdbool.h

*********************************************************************************/
typedef unsigned char                   Boolean;

See also the Xcode 7 Release Notes:

The type Boolean in MacTypes.h is imported as Bool in contexts that
allow bridging between Swift and Objective-C types.

In cases where the representation is significant, Boolean is imported
as a distinct DarwinBoolean type, which is BooleanLiteralConvertible
and can be used in conditions (much like the ObjCBool type).
(19013551)

As an example, the functions

void myFunc1(Boolean b);
void myFunc2(Boolean *b);

are imported to Swift as

public func myFunc1(b: Bool)
public func myFunc2(b: UnsafeMutablePointer<DarwinBoolean>)

In myFunc1 there is an automatic conversion between the native
Swift type Bool and the Mac Type Boolean.
This is not possible in myFunc2 because the address of a variable
is passed around, here DarwinBoolean is exactly the Mac Type Boolean.

In previous versions of Swift – if I remember correctly – this mapped
type was called Boolean, and has been renamed to DarwinBoolean later.

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More about ObjCBool:
ObjCBool is the Swift mapping of the Objective-C type BOOL,
this can be signed char or the C/C++ bool type, depending on the
architecture. For example, the NSFileManager method

- (BOOL)fileExistsAtPath:(NSString *)path
         isDirectory:(BOOL *)isDirectory

is imported to Swift as

func fileExistsAtPath(_ path: String,
      isDirectory isDirectory: UnsafeMutablePointer<ObjCBool>) -> Bool

Here the BOOL return value is converted to Bool automatically,
but the (BOOL *) is kept as UnsafeMutablePointer<ObjCBool>
because it is the address of a variable.

Cannot convert value of type 'Int' to raw type 'DarwinBoolean'

Ok so we have fixed this issue. The error message proved to be quite unhelpful as expected.

The issue turned out to be quite a stupid one. The orderService mentioned above had a method declared in the .h file which was unimplemented in the .m file and never used. The fact that it was unimplemented seems to have triggered the compiler error with the incredibly unhelpful message about Int not being convertible to DarwinBoolean.

Removing the declaration in the header file (or implementing the unneeded methods) solved the issue.

Swift Booleans not working: Cannot assign value of type 'Bool' to type 'BOOL' (aka 'Int32')

The solution for this problem was to disable optimizations in the build settings (from "optimize for speed" to "no optimization").

Cannot assign value of type UnsafeMutablePointer ObjCBool in Swift

I've never seen anything like the situation you describe, and personally I'm tempted to say the situation doesn't exist; I have never seen a BOOL* property or ivar in Objective-C in my life (and I'm darned old, believe me). However, if you insist: I haven't tested this, but I think you could say something like this:

var ok = UnsafeMutablePointer<ObjCBool>.alloc(1)
ok[0] = false // or true
let val = ok
myClass.isSSNField = val

However, although I think that will compile, I'm rather unclear on what the implications of doing it would be. It could cause the universe to collapse to a black hole, so be careful.

Swift closure: Cannot convert value of type '(_) - Bool' to expected argument type

Something flakey is happening with Swift's type inference. Give card an explicit type and it will work.

return hand.filter({ (card: Card) -> Bool in return card.type == .Red })

You don't need the return type or the return:

return hand.filter({ (card: Card) in card.type == .Red })

Note: this works also:

return hand.filter({ ($0 as Card).type == .Red })

Fully specifying the .Red enum value resolves the issue as well:

return hand.filter({ $0.type == Card.CardType.Red })

It was mentioned in the comments that if you move the definition of Card into the same file as the filter, that it works. In fact, if you split the definition of the CardType enum out from Card and just move CardType into the file with the filter, it works.

Representing NULL Function Pointers to C Functions in Swift

The Swift mapping of the (Objective-)C declaration

extern void _NSSetLogCStringFunction(void(*)(const char*, unsigned, BOOL));

is

public func _NSSetLogCStringFunction(_: (@convention(c) (UnsafePointer<Int8>, UInt32, ObjCBool) -> Void)!)

The easiest solution would be to put the Objective-C extern
declaration into an Objective-C header file and include that
from the bridging header.

Alternatively, in pure Swift it should be

typealias NSLogCStringFunc = @convention(c) (UnsafePointer<Int8>, UInt32, ObjCBool) -> Void

@_silgen_name("_NSSetLogCStringFunction")
func _NSSetLogCStringFunction(_: NSLogCStringFunc!) -> Void

In either case, the function parameter is an implicitly unwrapped optional,
and you can call it with nil. Example:

func myLogger(message: UnsafePointer<Int8>, _ length: UInt32, _ withSysLogBanner: ObjCBool) -> Void {
    print(String(format:"myLogger: %s", message))
}

_NSSetLogCStringFunction(myLogger) // Set NSLog hook.
NSLog("foo")
_NSSetLogCStringFunction(nil) // Reset to default.
NSLog("bar")

Output:

myLogger: foo
2016-04-28 18:24:05.492 prog[29953:444704] bar

How to retrieve a value from Firestore to change the text of button in table cell for every listen item?

Add something like this on the top of cellForRowAt

let thisComment = self.comments[indexPath.row]
let checkl1value = thisComment.checkl1value

Comments not Purple coloured when using /// in Xcode (swift)

The color of the documentation markups can be found in the Xcode preferences (tab "Fonts & Colors", line "Documentation Markup").

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