libzypp 17.31.7
zypp::callback Namespace Reference

Callbacks light. More...

## Classes

struct  DistributeReport

struct  ReportBase

struct  SendReport

struct  TempConnect
Temporarily connect a ReceiveReport then restore the previous one. More...

class  UserData
Typesafe passing of user data via callbacks. More...

## Detailed Description

Callbacks light.

The task report structure (SENDER SIDE).

A default constructible struct derived from callback::ReportBase. It must not contain any data, just virtual methods.

These are the functions the sender invokes, and which will be forwarded to some receiver. If no receiver is present, the defined default implementations are invoked.

For methods returning non-void, define a reasonable return value, because this is what you get back in case no receiver is listening.

This way, the sending side does not need to know whether some receiver is listening, and it enables the receiver to return a reasonable value in case it has got no idea what else to return.

struct Foo : public callback::ReportBase
{
virtual void ping( int i )
{}
virtual int pong()
{ return -1; }
};
Sending a Task report (SENDER SIDE).

Simply create a callback::SendReport<TReport>, where TReport is your task report structure. Invoke the callback functions as needed. That's it.

Note
Even creation and destruction of a callback::SendReport are indicated to a receiver. So even in case of an Exception, the receiver is able to recognize, that the task ended. So don't create it without need.
{
report->ping( 13 );
int response = report->pong();
}

To receive task reports of type Foo the recipient class derives from callback::ReceiveReport<Foo>. callback::ReceiveReport inherits Foo and provides two additional virtual methods:

virtual void reportbegin() {}
virtual void reportend() {}

These two are automatically invoked, whenever the sender creates a callback::SendReport instance, and when it gets destructed. So even if the sending task is aborted without sending an explicit notification, the reciever may notice it, by overloading reportend.

Overload the methods you're interested in.

Note
In case you must return some value and don't know which, return the task structures default. The author of the task structure had to provide this value, so it's probably better than anything you invent.
int somefunction()
{
...// don't know what to return?
return Foo::somefunction();
}

For this callback::ReceiveReport provides 4 methods:

void connect();
void disconnect();
bool connected() const;
• connect Connect this ReceiveReport (in case some other ReceiveReport is connected, it get disconnected. Remember it is a Callback light).
• disconnect Disconnect this ReceiveReport in case it is connected. If not connected, nothing happens.
• connected Test whether this ReceiveReport is currently connected.
• whoIsConnected Return a 'ReceiveReport*' to the currently connected ReceiveReport, or NULL if none is connected.
Passing Userdata via Callbacks

For typesafe passing of user data via callbacks,