Call a selector that takes a char* from PyObjC

Question

I'm trying to use a private framework with PyObjC. I've got this so far:

from AppKit import *
from Foundation import *
import objc

framework="/System/Library/PrivateFrameworks/DSObjCWrappers.framework"
objc.loadBundle("DSObjCWrapper", globals(), framework)

directory = DSoDirectory.alloc()
directory.initWithHost_user_password_("server", "diradmin", "password")

eDSStartsWith = 0x2002
node = directory.findNode_matchType_(u"/LDAPv3", eDSStartsWith)

That works fine. Now, I want to call a method on my node (of class DSoNode), with this objective-c signature.

• (BOOL) hasRecordsOfType:(const char*) inType

The most obvious way doesn't know how to take a string and pass it to a char*:

node.hasRecordsOfType_("dsRecTypeStandard:ComputerLists")
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)

/Users/clinton/<ipython console> in <module>()

ValueError: depythonifying 'char', got 'str' of 31

It looks like it is possible to change the signature as python sees it. I tried some variations on:

objc.registerMetaDataForSelector("DSoNode", "hasRecordsOfType_", dict( arguments={ 2+0: dict(type_modifier='n', type='^C') }))

but--and frankly I don't know how the registerMetaDataForSelector function works, and haven't found docs on it--I still get the same error when I invoke my selector on the node. How do I tell PyObjC to convert a string to a char*? (Or is there a better way to do it, as these strings are C constants #defined in a header file.)

---

Update: I tried using gen_bridge_metadata (as mentioned in this blog post), and, after consulting the man page, tried it as follows:

sudo mkdir -p /System/Library/PrivateFrameworks/DSObjCWrappers.framework/Resources/BridgeSupport
sudo gen_bridge_metadata --framework ~/Downloads/DSTools-112.1/build/Deployment/DSObjCWrappers.framework/ --output /System/Library/PrivateFrameworks/DSObjCWrappers.framework/Resources/BridgeSupport/DSObjCWrappers.bridgesupport

I still get the same error; there is no indication that this was even noticed, except that if I type:

help(modules)

I get:

/System/Library/PrivateFrameworks/DSObjCWrappers.framework/Versions/A/Resources/<ipython console> in <module>()

NameError: name 'modules' is not defined

I should also mention that I found a list of types that I believe would be understood by the registerMetaDataForSelector function; objective-C type encodings. Note that the XML for the particular function I'm after says:

<method selector='hasRecordsOfType:'>
<retval type='B'/>
</method>

I would've expected something explaining the input parameter, too.

Answer 1

I believe you want the following and then should pass a non-unicode string:

objc.registerMetaDataForSelector("DSoNode",
                                 "hasRecordsOfType:",
            dict(
                arguments =
                {
                    2: dict(type=objc._C_PTR + objc._C_CHAR_AS_TEXT,
                            c_array_delimited_by_null=True,
                            type_modifier=objc._C_IN)
                }
            ))

---

A more complete NSString example follows:

from AppKit import *
from Foundation import *
import objc

def setupMetadata():
    objc.registerMetaDataForSelector("NSString", "stringWithCString:",
        dict(
            arguments =
            {
                2: dict(type=objc._C_PTR + objc._C_CHAR_AS_TEXT,
                        c_array_delimited_by_null=True,
                        type_modifier=objc._C_IN)
            }
        ))

def doTest():
    s = NSMutableString.stringWithString_(u"foo");
    NSLog(u"string[" + s + "]")

    s2 = NSString.stringWithCString_("bar")
    NSLog(u"string[" + s2 + "]")

setupMetadata()
doTest()

Answer 2

You have to call hasRecordsOfType like so:

from ctypes import *

typeString = c_char_p('dsRecTypeStandard:ComputerLists')
node.hasRecordsOfType_(typeString)