swift - How to create a UnsafeMutablePointer<UnsafeMutablePointer<UnsafeMutablePointer<Int8>>> -

i'm working c api swift , 1 of methods need call need give a

unsafemutablepointer<unsafemutablepointer<unsafemutablepointer<int8>>> 

more info:

swift interface:

public func presage_predict(prsg: presage_t, _ result: unsafemutablepointer<unsafemutablepointer<unsafemutablepointer<int8>>>) -> presage_error_code_t 

original c:

presage_error_code_t presage_predict(presage_t prsg, char*** result); 

generally, if function takes unsafepointer<t> parameter can pass variable of type t in "inout" parameter &. in case, t is

unsafemutablepointer<unsafemutablepointer<int8>> 

which swift mapping of char **. can call c function as

var prediction : unsafemutablepointer<unsafemutablepointer<int8>> = nil if presage_predict(prsg, &prediction) == presage_ok { ... } 

from documentation , sample code of presage library understand allocates array of strings , assigns address of array variable pointed prediction. avoid memory leak, these strings have released

presage_free_string_array(prediction) 

to demonstrate works, have taken first part of demo code @ presage_c_demo.c , translated swift:

// duplicate c strings avoid premature deallocation: let past = strdup("did not sa") let future = strdup("")  func get_past_stream(arg: unsafemutablepointer<void>) -> unsafepointer<int8> {     return unsafepointer(past) }  func get_future_stream(arg: unsafemutablepointer<void>) -> unsafepointer<int8> {     return unsafepointer(future) }  var prsg = presage_t() presage_new(get_past_stream, nil, get_future_stream, nil, &prsg)  var prediction : unsafemutablepointer<unsafemutablepointer<int8>> = nil if presage_predict(prsg, &prediction) == presage_ok {      var = 0; prediction[i] != nil; i++ {         // convert c string swift `string`:         let pred = string.fromcstring(prediction[i])!         print ("prediction[\(i)]: \(pred)")     }      presage_free_string_array(prediction) }  free(past) free(future) 

this worked , produced output

 prediction[0]: prediction[1]: said prediction[2]: savages prediction[3]: saw prediction[4]: sat prediction[5]: same