objp / README

ObjP's goal is to create a two-way bridge between Python and Objective-C. Unlike PyObjC, which uses
dynamic calls to methods on runtime, ObjP generates static code. It generates either Objective-C
interfaces to Python code or Python modules to interface Objective-C code.

The library is exceedingly simple and it's intended that way. Unlike PyObjC, there's no way ObjP
could possibly wrap the whole Cocoa framework, there's way too many things to support. ObjP is made
to allow you to bridge your own code.

Also note that ObjP works on Python 3.2 and up.

The best way to learn how to use ObjP is, I think, to look at an example. There are many of them in
the 'demos' subfolder. These are built using ``waf`` (it's already included in here, no need to
install it). For example, if you want to build the ``simple`` demo, do::

    $ cd demos/simple
    $ ./waf configure build
    $ cd build
    $ ./HelloWorld

That programs calls a simple Python script from Objective-C, and that python script itself calls
an Objective-C class.


There are two types of bridge: Objective-C class wrapping a Python class (o2p) and Python class
wrapping an Objective-C class (p2o).

To generate an o2p wrapper, you need a target class. Moreover, for this class' methods to be
wrapped, you need to have its arguments and return value correctly annotated (You can browse the
demos for good examples of how to do it). This is an example of a correctly annotated class::

    class Foo:
        def hello_(self, name: str) -> str:
            return "Hello {}".format(name)

To wrap this class, you'll use ``objp.o2p.generate_objc_code()`` in this fashion::

    import foo
    import objp.o2p
    objp.o2p.generate_objc_code(foo.Foo, 'destfolder')

This will generate "Foo.h|m" as well as "ObjP.h|m" in "destfolder". These source files directly
use the Python API and have no other dependencies.

To generate a p2o wrapper, you either need an Objective-C header file containing an interface or
protocol or a Python class describing that interface::

    @interface Foo: NSObject {}
    - (NSString *)hello:(NSString *)name;

To generate a python wrapper from this, you can do::

    import objp.p2o
    objp.p2o.generate_python_proxy_code(['Foo.h'], 'destfolder/Foo.m')

This will generate the code for a Python extension module wrapping ``Foo``. The name of the
extension module is determined by the name of the destination source file. You can wrap more than
one class in the same unit::

    objp.p2o.generate_python_proxy_code(['Foo.h', 'Bar.h'], 'destfolder/mywrappers.m')

Method name conversion

ObjP follows PyObjC's convention for converting method names. The ":" character being illegal in
Python method names, they're replaced by underscores. Thus, a method
``- (BOOL)foo:(NSInteger)arg1 bar:(NSString *)arg2;`` is converted to
``def foo_bar_(self, arg1: int, arg2: str) -> bool:`` and vice versa.

Note that if your method's argument count doesn't correspond to the number of underscores in your
method name, objp will issue a warning and ignore the method.

Argument Types

Only a few argument types are supported by ObjP, the goal being to keep the project simple.

* ``int/NSInteger``
* ``float/CGFloat``
* ``str/NSString*``
* ``bool/BOOL``
* ``list/NSArray*``
* ``dict/NSDictionary*``

ObjP also supports ``object`` which dynamically converts the argument depending on its type and
returns an ``NSObject`` subclass (which means that ``int``, ``float`` and ``bool` convert to
``NSNumber`` instead of converting to ``NSInteger`` and ``BOOL``). This type of conversion is used
to convert the contents of ``list`` and ``dict`` (it's impossible to have an NSArray directly
containing ``BOOL``).

Another special argument type is ``pyref`` (which you must import from ``objp.util`` in your code)
which simply passes the ``PyObject*`` instance around without converting it.


``objp.util`` contains the ``pyref`` argument type, but it also contains two useful method
decorators: ``dontwrap`` and ``objcname``. A method decorated with ``dontwrap`` will be ignored by
the code generator, and a method decorated with ``@objcname('some:selector:')`` will use this name
for generating objc code instead of the automatically generated name.
Tip: Filter by directory path e.g. /media app.js to search for public/media/app.js.
Tip: Use camelCasing e.g. ProjME to search for
Tip: Filter by extension type e.g. /repo .js to search for all .js files in the /repo directory.
Tip: Separate your search with spaces e.g. /ssh pom.xml to search for src/ssh/pom.xml.
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