If you are using Xcode 8 or above, you can use the memory graph thingy to see what object holds a reference to what object. To see the memory graph, first build and run your app with Xcode. When you want to check whether all the instances you created are discarded properly, go to this … Read more
shared_ptr uses an extra “counter” object (aka. “shared count” or “control block”) to store the reference count. (BTW: that “counter” object also stores the deleter.) Every shared_ptr and weak_ptr contains a pointer to the actual pointee, and a second pointer to the “counter” object. To implement weak_ptr, the “counter” object stores two different counters: The … Read more
When a listener attaches an event listener to an event, the source object will get a reference to the listener object. This means that the listener cannot be collected by the garbage collector until either the event handler is detached, or the source object is collected. Consider the following classes: class Source { public event … Read more
Bitmap.recycle isn’t required to be called, as the garbage collector will clean up bitmaps on its own eventually (as long as there are no references). Bitmaps in Android are created in native memory, not on the VM heap, so the actual bitmap object on the VM heap is very small as it doesn’t contain any … Read more
Update: Since July, 2020 some implementations (Chrome, Edge, Firefox and Node.js) has had support for WeakRefs as defined in the WeakRefs proposal, which is a “Stage 3 Draft” as of December 16, 2020. There is no language support for weakrefs in JavaScript. You can roll your own using manual reference counting, but not especially smoothly. … Read more
First of all, note that you generally don’t need to worry about retain cycles with DispatchQueue.main.asyncAfter, as the closure will be executed at some point. Therefore whether or not you weakly capture self, you won’t be creating a permanent retain cycle (assuming that tickle.fresh also doesn’t). Whether or not you put a [weak self] capture … Read more
Using a WeakReference in Android isn’t any different than using one in plain old Java. You should think about using one whenever you need a reference to an object, but you don’t want that reference to protect the object from the garbage collector. A classic example is a cache that you want to be garbage … Read more
Java provides two different types/classes of Reference Objects: strong and weak. Weak Reference Objects can be further divided into soft and phantom. Strong Weak soft phantom Let’s go point by point. Strong Reference Object StringBuilder builder = new StringBuilder(); This is the default type/class of Reference Object, if not differently specified: builder is a strong … Read more
tl; dr: The problem is that the string literal never gets released so your weak pointer still points to it. Theory Strong variables will retain the value they point to. Weak variables won’t retain their value and when the value is deallocated they will set their pointer to nil (to be safe). Unsafe unretained values … Read more
From the assembly code it can be seen that accessing weakPtr generates a objc_loadWeak call. According to the Clang documentation, objc_loadWeak retains and autoreleases the object and is equivalent to id objc_loadWeak(id *object) { return objc_autorelease(objc_loadWeakRetained(object)); } This (hopefully) explains why both if(strongPtr == weakPtr) … and NSLog(@”weakPtr: %@”, weakPtr); create additional autoreleased references. This … Read more