There is no “callback” in C – not more than any other generic programming concept. They’re implemented using function pointers. Here’s an example: void populate_array(int *array, size_t arraySize, int (*getNextValue)(void)) { for (size_t i=0; i<arraySize; i++) array[i] = getNextValue(); } int getNextRandomValue(void) { return rand(); } int main(void) { int myarray[10]; populate_array(myarray, 10, getNextRandomValue); … … Read more
You can do that if the member function is static. Non-static member functions of class A have an implicit first parameter of type class A* which corresponds to this pointer. That’s why you could only register them if the signature of the callback also had the first parameter of class A* type.
Activity involved is completely unaware of the DialogFragment. Fragment class: public class MyFragment extends Fragment { int mStackLevel = 0; public static final int DIALOG_FRAGMENT = 1; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); if (savedInstanceState != null) { mStackLevel = savedInstanceState.getInt(“level”); } } @Override public void onSaveInstanceState(Bundle outState) { super.onSaveInstanceState(outState); outState.putInt(“level”, mStackLevel); } void … Read more
var myCallback = function(data) { console.log(‘got data: ‘+data); }; var usingItNow = function(callback) { callback(‘get it?’); }; Now open node or browser console and paste the above definitions. Finally use it with this next line: usingItNow(myCallback); With Respect to the Node-Style Error Conventions Costa asked what this would look like if we were to honor … Read more
async/await is not magic. An async function is a function that can unwrap Promises for you, so you’ll need api.on() to return a Promise for that to work. Something like this: function apiOn(event) { return new Promise(resolve => { api.on(event, response => resolve(response)); }); } Then async function test() { return await apiOn( ‘someEvent’ ); … Read more
Actually, your code will pretty much work as is, just declare your callback as an argument and you can call it directly using the argument name. The basics function doSomething(callback) { // … // Call the callback callback(‘stuff’, ‘goes’, ‘here’); } function foo(a, b, c) { // I’m the callback alert(a + ” ” + … Read more
In Javascript, there are synchronous and asynchronous functions. Synchronous Functions Most functions in Javascript are synchronous. If you were to call several synchronous functions in a row doSomething(); doSomethingElse(); doSomethingUsefulThisTime(); they will execute in order. doSomethingElse will not start until doSomething has completed. doSomethingUsefulThisTime, in turn, will not start until doSomethingElse has completed. Asynchronous Functions … Read more
For a comprehensive explanation of why this happens, see this Q/A, and this one. Basically, at the time you set the new style the browser still has not applied the one set inline, your element’s computed style still has its display value set to “” , because it’s what elements that are not in the … Read more
The point seems to be that sometimes, you need a property that has automatic storage and some behavior, for instance to notify other objects that the property just changed. When all you have is get/set, you need another field to hold the value. With willSet and didSet, you can take action when the value is … Read more
Instead of having static methods and passing around a pointer to the class instance, you could use functionality in the new C++11 standard: std::function and std::bind: #include <functional> class EventHandler { public: void addHandler(std::function<void(int)> callback) { cout << “Handler added…” << endl; // Let’s pretend an event just occured callback(1); } }; The addHandler method … Read more