How to automatically select and change a custom keyboard on iOS App

Question

i already got list of installed custom keyboard using under code but how can i select specific custom keyboard.

[UITextInputMode activeInputModes];

I want to select my custom keyboard when open my app,But I haven't found a way to make the system automatically choose to use my keyboard.

I have tried the following methods, but none of them work,likes this:

[UITextInputMode setValue:@[myInputModel] forKey:@"activeInputModes"];

or

[UITextInputMode setValue:myInputModel forKey:@"currentInputMode"];