Class CommandChainDispatcher

IPython/core/hooks.py:89–132

Dispatch calls to a chain of commands until some func can handle it Usage: instantiate, execute "add" to add commands (with optional priority), execute normally via f() calling mechanism.

class CommandChainDispatcher:
    """ Dispatch calls to a chain of commands until some func can handle it

    Usage: instantiate, execute "add" to add commands (with optional
    priority), execute normally via f() calling mechanism.

    """
    def __init__(self,commands=None):
        if commands is None:
            self.chain = []
        else:
            self.chain = commands


    def __call__(self,*args, **kw):
        """ Command chain is called just like normal func.

        This will call all funcs in chain with the same args as were given to
        this function, and return the result of first func that didn't raise
        TryNext"""
        last_exc = TryNext()
        for prio,cmd in self.chain:
            #print "prio",prio,"cmd",cmd #dbg
            try:
                return cmd(*args, **kw)
            except TryNext as exc:
                last_exc = exc
        # if no function will accept it, raise TryNext up to the caller
        raise last_exc

    def __str__(self):
        return str(self.chain)

    def add(self, func, priority=0):
        """ Add a func to the cmd chain with given priority """
        self.chain.append((priority, func))
        self.chain.sort(key=lambda x: x[0])

    def __iter__(self):
        """ Return all objects in chain.

        Handy if the objects are not callable.
        """
        return iter(self.chain)


def shutdown_hook(self):