| rdfs:comment
| - Callbacks are members of objects that are called internally by ROBLOX in certain situations. There are currently only two callbacks in the entire ROBLOX API. These are the RequestShutdown callback of the DataModel and the OnInvoke callback of the BindableFunction object. There was also previously another callback, called "Receive", which belonged to CustomEvents, but it was removed and was instead replaced by an event.
- The CallBack coordination style differs from the Master Worker style with respect to only one aspect, i.e., the block of business logic written in a CallBack method call is executed only if the result of the callback method call is non erroneous. Syntax: Callback(agent | component.methodName(param_list); variable of method’s return type) { // business logic } where,
* agent and component are instances of type Agent and Component
- A callback, function object, function pointer, or delegate is a value which represents a subroutine and is passed from one bit of code to another, in the process being assigned to a different variable. This is accomplished in different ways across languages: Callbacks are used in cases where some of the logic is specified in user code, such as event-handling. Normally the callback is written within user code and passed as an argument to a library function, but sometimes a callback will instead be returned from a function for user code to call (or not) when appropriate.
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| abstract
| - Callbacks are members of objects that are called internally by ROBLOX in certain situations. There are currently only two callbacks in the entire ROBLOX API. These are the RequestShutdown callback of the DataModel and the OnInvoke callback of the BindableFunction object. There was also previously another callback, called "Receive", which belonged to CustomEvents, but it was removed and was instead replaced by an event.
- A callback, function object, function pointer, or delegate is a value which represents a subroutine and is passed from one bit of code to another, in the process being assigned to a different variable. This is accomplished in different ways across languages:
* Lisp, JavaScript, and Python functions are first-class values, which in the latter two makes them objects.
* C and C++ simply apply the concept of a pointer to functions.
* Visual Basic uses the Delegate modifier to allow the use of a Sub procedure as a type.
* Java performs reflection via a section of its standard library, which may be clumsily used to find and call a method whose name is in a string.
* PHP provides anonymous functions and a small "Function Handling" API, a much simpler implementation of reflection than that of Java. Callbacks are used in cases where some of the logic is specified in user code, such as event-handling. Normally the callback is written within user code and passed as an argument to a library function, but sometimes a callback will instead be returned from a function for user code to call (or not) when appropriate. For example, given the following filter function in pseudocode: list filter(list l, delegate f) initialize list r for i = 0 to l.count - 1 if f.invoke(l[i]) = true then r.add l[i] return r We can put in any type of filtering method that we like to pass to the function. For example, given a function that will return true if the passed number is greater than 9: boolean gr(int x) return x > 9 You can use this to get all numbers greater than 9 on the list: // given a list somelist delegate pfilter = reference to gr list result = filter(somelist, pfilter)
- The CallBack coordination style differs from the Master Worker style with respect to only one aspect, i.e., the block of business logic written in a CallBack method call is executed only if the result of the callback method call is non erroneous. Syntax: Callback(agent | component.methodName(param_list); variable of method’s return type) { // business logic } where,
* agent and component are instances of type Agent and Component Unlike the Broadcast, Blackboard/Agenda or Parallel Pipe styles of coordination, using Callback does not identify the responder's role and id since invoking a single, and not multiple or arrays of, agent or component instances is possible in Callback. public Agent CallbackAgent { public void setValue(int x); public int getValue(); public void incrValue(); } Definition file : CallbackAgent.indus public class CallbackClass implements CallbackAgent { Context{ setServantType("USER"); } public int m_value = 0; public int getValue() { return m_value; } public void setValue(int v) { m_value = v; } public void incrValue() { m_value++; } public static void main(String [] args) { try { CallbackClass m = newType CallbackClass("cb1"); int value = 0; Callback(m.getValue();value) { System.out.println("value = " + value); } Callback(m.setValue(100);) {} Callback(m.getValue();value) { System.out.println("value = " + value); } Callback(m.incrValue();) {} Callback(m.getValue();value) { System.out.println("value = " + value); } Callback(m.incrValue();) {} Callback(m.getValue();value) { System.out.println("value = " + value); } } catch (Exception e) { e.printStackTrace(); } } } Implementation file : CallbackClass.indus
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