PyObjC provides transparant conversion or proxying of values between Python and Objective-C. In general this works as expected, this document provides a detailed guide to how values are converted or proxied.
The Objective-C language not only has classes and objects, but also has the basic C types which are not classes. PyObjC converts between those and the corresponding Python type.
The C type ‘char’ does not have a unambigous meaning in C, it is used for a number of tasks. In the table below the various tasks have been represented separately: booleans (BOOL), representing characters in text (char) and represeting small integers (int8_t). PyObjC uses metadata in the framework wrappers to know when to use which representation.
C type | Python 2.x | Python 3.x |
---|---|---|
int8_t | int | int |
BOOL | bool | bool |
char | str of len(1) | bytes of len(1) |
unsigned char | int | int |
short | int | int |
unsigned short | int | int |
int | int | int |
unsigned int | int | int |
int | int | int |
unsigned int | int or long | int |
long | int | int |
unsigned long | int or long | int |
long long | int or long | int |
unsigned long long | int or long | int |
float | float | float |
double | float | float |
PyObjC does range checking when converting values to C, and will raise ValueError when the input value is out of range.
PyObjC will accept negative values when converting a Python numeric value to an unsigned integer value. This is done due to limitations in the metadata creation process, sometimes constant values that are used with unsigned integer arguments are represented as negative values in the metadata files. This feature will be fixed in a future version of PyObjC and users should therefore not rely on being able to convert negative values to an unsigned integer type.
TDB
TDB
PyObjC cannot convert to and from C union types at the moment.
TBD
TBD