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Use a C function in Swift

I want to use a C function in Swift that has the following method definition:

int startTest(char *test1, char* test2)

If I call this method from my Swift code like this

startTest("test1", "test2")

The following error message appears:

'String' is not convertible to 'UnsafeMutablePointer<Int8>'

If I change my method definition to:

int startTest(const char *test1, const char* test2)

and call this method like this:

var test1 = "test1"
var test2 = "test2"
startTest(&test1, &test2)

I get

'String' is not identical to 'Int8'

So my question is, how can I use the C function? (this is part of the library, so changing the method call can be problematic).

Thanks in advance!

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1 answer


When

int startTest(const char *test1, const char* test2);

you can call a function from Swift just like

let result = startTest(test1, test2)

(without operator addresses). Swift strings are converted automatically to C Strings for function calls



When

int startTest(char *test1, char* test2);

you need to call the function with a buffer (variable) Int8

because the Swift compiler has to assume that strings can be modified from within a C function.

Example:

var cString1 = test1.cStringUsingEncoding(NSUTF8StringEncoding)!
var cString2 = test2.cStringUsingEncoding(NSUTF8StringEncoding)!
let result = startTest(&cString1, &cString2)
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