I have the following code in Objective-C:
- (double)readDouble
{
double value = 0.0;
if ([self read:(uint8_t *)&value maxLength:8] != 8)
{
NSLog(@"***** Couldn't read double");
}
return value;
}
It works. But I don't know how to convert it to Swift. Here is my code:
public func readDouble() -> Double {
var value : Double = 0.0
var num = self.read((uint8_t *)&value, maxLength:8) // got compiling error here!
if num != 8 {
}
}
The error message is:
Cannot invoke '&' with an argument list of type '($T4, maxLength: IntegerLiteralConvertible)'
Can anybody help? Thanks
The testing data I'm using (1.25):
14 AE 47 E1 7A 14 F4 3F
UPDATE:
A simple c solution, but how to do this in Swift?
double d = 0;
unsigned char buf[sizeof d] = {0};
memcpy(&d, buf, sizeof d);
This should work:
Explanation:
withUnsafeMutablePointer()
calls the closure (block) with the only argument ($0
in shorthand notation) set to the address ofvalue
.$0
has the typeUnsafeMutablePointer<Double>
andread()
expects anUnsafeMutablePointer<UInt8>
as the first argument, therefore another conversion is necessary. The return value of the closure is then assigned tonum
.The method above does not work for me, using Swift 2 but I discovered a much more simpler method to do this conversion and vice versa:
I have tested it with Xcode 7.2 in the playground.
Here is the updated version for Swift 3 beta 6 which is different, thanx to Martin.