Objective-C nil / Nil / NULL /NSNull
March 7, 2016
JRiOSios, objective cLeave a comment
Here are some notes from Mattt excellent write up on nil / Nil and Null.
Read the full post here.
Read more here http://nshipster.com/nil/
C represents nothing as 0 for primitives, NULL, for pointers.
Objective-C nothing is nil. nil is an object pointer to nothing.Although semantically distinct from NULL, they are technically equivalent to one another.
On the framework level, Foundation defines NSNull, which defines a class method +null, which defines the singleton NSNull object. NSNull is different from nil or NULL, in that it is an actual object, rather than a zero value.
Foundation/NSObjcCRuntime.h also defines Nil as a class pointer to nothing. This lesser-known title-case cousin of nil doesn’t show up much very often, but it’s at least worth nothing.
Newly alloc’d NSObjects start life off with their contents set to 0. This means that all points that object has to other points bigs as nil.
Most notable behavior of nil, though, is that is can have messages sent to it. This would crash other programs in C++. Which greatly simplifies expressions, as it obviates the need to check for nil before doing anything.
FAQs
In Objective-C: nil is a pointer to a non-existent object. In Swift: nil is not a pointer, it's the absence of a value of a certain type. NULL and nil are equal to each other, but nil is an object value while NULL is a generic pointer value ((void*)0, to be specific).
How to handle null in Objective-C? ›
In Objective-C, you work with references to objects by using pointers that can be null, called nil in Objective-C. In Swift, all values — including object instances — are guaranteed to be non-null. Instead, you represent a value that could be missing as wrapped in an optional type.
Is Nil false in Objective-C? ›
In Objective-C, all objects are accessed via pointers, and nil is actually a pointer with a value of zero. Thus, when an object is assigned a value of nil, it is actually given a pointer with a value of 0, indicating that the object does not exist.
What is the difference between null and Nullptr in Objective-C? ›
Nullptr vs NULL
NULL is 0 (zero) i.e. integer constant zero with C-style typecast to void* , while nullptr is prvalue of type nullptr_t , which is an integer literal that evaluates to zero.
What is the difference between nil and NSNull in Objective-C? ›
If nil is the essence of nothingness itself, NSNull is a representation of nothingness. NSNull contains a method null whose only purpose is to give you a singleton to a representation, or placeholder, of nothingness.
What is NSNull? ›
A singleton object used to represent null values in collection objects that don't allow nil values.
What is the best way to handle null values? ›
If the null values are due to technical problems or if they are important to the analysis, you may want to impute them. This means replacing the missing values with estimated values. There are a variety of imputation methods available, such as mean imputation, median imputation, and regression imputation.
What can I use instead of null in C? ›
- In almost all cases NULL should be replaced in modern C++ code with nullptr. ...
- NULL should be used when interfacing with legacy C code that expects it. ...
- nullptr is explicitly excluded from being converted to an integer value, the compiler will complain.
We can use the @JsonInclude Annotation to ignore the null values at the class or property level.
Why nil instead of null? ›
nil is an identifier for the zero value in many of the language's types. It's reminiscent of null in other languages, but it would be a mistake to treat them the same way. nil is not null .
Objective-C's syntax is notorious for its complexity and verbosity. The language is filled with square brackets and semicolons, making it difficult for developers to focus on the core of the code.
What are the drawbacks of Objective-C? ›
2. Disadvantages of Objective-C
- 2.1 Complex and Outdated Syntax. ...
- 2.2 Lower Performance Compared to Swift. ...
- 2.3 Lack of New Improvements. ...
- 2.4 Lack of Safety. ...
- 2.5 Declining Community. ...
- 2.6 Learning and Usage Difficulty.
Using Length Property. One of the simplest and most effective ways to check if an NSString is empty is by using the length property. This method not only checks for an empty string ( @"" ) but also handles nil values. This approach is straightforward and covers the most common cases.
Is it better to use null or nullptr? ›
The difference is that NULL is an integer, nullptr is a pointer type. It is a crucial difference when dealing with (resolving) method overloads. They are not interchangeable*). When you talk pointer, always use nullptr.
Can I use 0 instead of nullptr? ›
You can use an integer constant expression with the value 0 or an expression that is cast to (void *)0 as a null pointer constant. The macro NULL and value 0 are equivalent as null pointer constants, but NULL is cleaner because it represents the purpose of using the constant for a pointer.
How to check if string is empty or nil in Objective-C? ›
One of the simplest and most effective ways to check if an NSString is empty is by using the length property. This method not only checks for an empty string ( @"" ) but also handles nil values.
What type of ID is Objective-C? ›
id automatically assumes a pointer, as all objects in Objective-C are passed as pointers/references. id is a data type of object identifiers in Objective-C, which can be use for an object of any type no matter what class does it have. id is the final super type of all objects.
Is null the same as nil? ›
They mean different things. Null is an adjective meaning 'invalid' or 'nonexistent. ' Nil is a noun meaning 'nothing' or 'nought'.
What are the Objective-C data type? ›
Objective-C supports integer data type. This data type stores the whole number, hexadecimal values, and octal values. We can determine the size of the integer type using sizeof the operator in Objective-C.
