Python调用PJSUA2的utilAddPendingJob方法遇类型错误求助

Let's break down what's causing that TypeError and fix it step by step:

The Root Causes #

Your issue stems from three key problems in your code and how SWIG handles C++ abstract classes in Python:

• Missing parent class initialization: Even though pj.PendingJob is marked as abstract by SWIG, your subclass needs to initialize the underlying C++ object by calling the parent constructor. Without this, SWIG can't wrap your Python object into a valid pj::PendingJob* pointer.
• Mismatched method signature: The execute method in your subclass doesn't match the exact signature of the pure virtual function in the C++ PendingJob class. SWIG relies on exact signature matches to recognize valid implementations of abstract methods.
• Invalid variable reference: You're trying to print text directly instead of accessing the instance variable with self.text (this would cause a NameError once the type issue is fixed).

Fixed Code #

Here's the corrected version of your code:

import pjsua2 as pj

class MyJob(pj.PendingJob):
    def __init__(self, text):
        # Initialize the parent class to create the underlying C++ object
        super().__init__()
        self.text = text
    
    # Exact match for the C++ method signature: no default parameters
    def execute(self, is_pending):
        print(self.text)

# Usage remains the same
job = MyJob("test")
pj.Endpoint.instance().utilAddPendingJob(job)

Explanation #

• Parent constructor call: The super().__init__() line might seem counterintuitive since SWIG's PendingJob.__init__ raises an error, but this is part of SWIG's abstraction layer. Calling it ensures the underlying C++ PendingJob instance is created, which is required for SWIG to convert your Python object to a valid C++ pointer.
• Signature consistency: The C++ PendingJob::execute expects a single boolean parameter with no default value. Removing the is_pending = False default in your Python method ensures SWIG recognizes it as a valid implementation of the pure virtual function.
• Instance variable access: Using self.text correctly references the instance variable you initialized in __init__, avoiding a NameError when the job executes.

SWIG handles abstract C++ classes in Python by requiring strict adherence to method signatures and proper initialization of parent classes. Fixing these points will resolve the type mismatch and let your pending job execute as expected.

内容的提问来源于stack exchange，提问作者Rob