How to Check if an NSString is Empty in Objective-C

How to Check if an NSString is Empty in Objective-C

6 June 2024 Stephan Petzl Leave a comment Tech-Help

When working with NSString in Objective-C, it’s often necessary to determine whether a string is empty. This guide provides several methods to achieve this, each with its own advantages. Let’s explore these solutions to help you find the one that best fits your needs.

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.

if ([myString length] == 0) {
    NSLog(@"String is empty.");

This approach is straightforward and covers the most common cases.

Trimming Whitespace

Sometimes, a string may contain only whitespace, which should be considered empty. To handle such cases, you can use the stringByTrimmingCharactersInSet: method to remove whitespace before checking the length.

NSString *trimmedString = [myString stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]];
if ([trimmedString length] == 0) {
    NSLog(@"String is empty or contains only whitespace.");

For convenience, you can define a macro to simplify this process:

#define allTrim( object ) [object stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]]
if ([allTrim(myString) length] == 0) {
    NSLog(@"String is empty or contains only whitespace.");

Using Categories

Another approach is to create a category on NSString to add a method that checks for whitespace and newline characters:

@implementation NSString (Empty)

- (BOOL)isWhitespace {
    return ([[self stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]] length] == 0);


This method extends the functionality of NSString, making it more versatile and reusable.

Generalized isEmpty Function

For a more comprehensive solution, you can use a generalized function that checks for various conditions, including nil, NSNull, and empty strings or collections:

static inline BOOL isEmpty(id thing) {
    return thing == nil
    || [thing isKindOfClass:[NSNull class]]
    || ([thing respondsToSelector:@selector(length)] && [(NSData *)thing length] == 0)
    || ([thing respondsToSelector:@selector(count)] && [(NSArray *)thing count] == 0);

This function is versatile and can be used to check the emptiness of different types of objects.


Checking if an NSString is empty in Objective-C can be done in several ways, depending on your specific requirements. Whether you are checking for nil values, trimming whitespace, or using a generalized function, these methods provide robust solutions for ensuring your strings are not empty.

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