What happens when you invoke a method on a nil pointer Objective-C?

In Objective-C, it is valid to send a message to nil — it simply has no effect at runtime. If the method returns any pointer type, any integer scalar of size less than or equal to sizeof(void*) , a float , a double , a long double , or a long long , then a message sent to nil returns 0 .

How do you check if a string is nil in Objective-C?

30 Answers. You can check if [string length] == 0 . This will check if it’s a valid but empty string (@””) as well as if it’s nil, since calling length on nil will also return 0.

How do I check if a variable is null in Objective-C?

If you treat it is a null string like nil , then test (object. length == 0) . object. length will return 0 if object == nil , so this test covers nil objects and strings with length 0.

What happens when you invoke a method on a nil pointer in Swift?

What happens when you invoke a method on a nil pointer in iOS? A message sent to a nil object is perfectly acceptable in Objective-C, it’s treated as a no-op. There is no way to flag it as an error because it’s not an error, in fact it can be a very useful feature of the language.

Why retainCount should never be used in shipping code?

You should never use -retainCount , because it never tells you anything useful. The implementation of the Foundation and AppKit/UIKit frameworks is opaque; you don’t know what’s being retained, why it’s being retained, who’s retaining it, when it was retained, and so on.

What is correct nil or nill?

Nilnoun. Nothing; of no account; worthless; – a term often used for canceling, in accounts or bookkeeping. Nillnoun. Scales of hot iron from the forge.

How does Objective C handle null values?

The NULL value for Objective-C objects (type id) is nil. While NULL is used for C pointers (type void *). nil = (all lower-case) is a null pointer to an Objective-C object. Nil = (capitalized) is a null pointer to an Objective-C class.

How check Textview is empty or not in Swift?

How to check if a text field is empty or not in swift?

1. Step 3 − Add IBOutlet for text field in ViewController, name it textField.
2. Step 4 − Add IBoutlet for label, it resultLabel.
3. Step 5 − Add @IBAction for touchUpInside ‘Check’ button as follows @IBAction func checkTextFeild(_ sender: Any) { }

What happens when you call retain on an object?

You send an object a retain message when you want to prevent it from being deallocated until you have finished using it. An object is deallocated automatically when its reference count reaches 0 . retain messages increment the reference count, and release messages decrement it.