Objective-C Data Types

In the Objective-C programming language, Objective-C data types refer to an extensive system used for declaring variables or functions of different types. The type of a variable determines how much space it occupies in storage and how the bit pattern stored is interpreted.

What are the main objective of data types?
Answer: A data type constrains the values that an expression, such as a variable or a function, might take. This data type defines the operations that can be done on the data, the meaning of the data, and the way values of that type can be stored.

What is a double in Objective-C?
The Objective-C double data type is used to store larger values than can be handled by the float data type. The term double comes from the fact that a double can handle values twice the size of a float.

What is primitive data type in Objective C?
There are two primitive floating point types available in Objective-C: The float type is a 32-bit single precision float point value that uses a single sign bit, an 8-bit mantissa and 23 bits of exponent when storing numbers.

The types in Objective-C can be classified as follows

Basic Types
-includes arithmetic types
-integer types and floating-point types

Enumerated types
-void typeindicates that no value is available

Derived types
-Pointer types
-Array types
-Structure types
-Union types
-Function types

int Data Type

int Data Type

int myoctal = 024;

char Data Type
char myChar = 'w';


Special Characters/Escape Sequences

float Data Type
float myfloat = 123.432f

double Data Type

id Data Type

BOOL Data Type

_Bool flag = 0;
BOOL secondflag = 1;

Objective-C Data Type Qualifiers

long 
long int mylargeint;

long long 
long long int mylargeint;

short 
short int myshort;

signed / unsigned
unsigned int myint;

long double 
long double mydouble;

Arrays

type arrayName [ arraySize ];
double myArray[5] = {1.0, 2.0, 3.4, 12.0, 52.0};

int n[ 10 ];
int i,j;

for ( i = 0; i < 10; i++ )
{
n[ i ] = i + 100; /* set element at location i to i + 100 */
}

for (j = 0; j < 10; j++ )
{
NSLog(@"Element[%d] = %d\n", j, n[j] );
}


NSArray *myArray;
myArray= [NSArray arrayWithObjects: object1, object2, object3, nil];
NSLog(@"Array contents = %@",[myArray componentsJoinedByString:@", "]); 

NSArray *myArray;
myArray= [NSArray arrayWithObjects: object1, object2, object3, nil];
for (NSString *randomVariable in myArray) 
{
NSLog (@"Array element = %@", randomVariable);
}  
NSArray *myArray;
myArray= [NSArray arrayWithObjects: object1, object2, object3, nil];
int i;
for (i = 0; i < [myArray count]; i++)
{
NSLog (@"Element %i = %@", i, [myArray objectAtIndex: i]); 
}

Pointers

type *var-name;

int    *ip;    /* pointer to an integer */
double *dp;    /* pointer to a double */
float  *fp;    /* pointer to a float */

char   *ch     /* pointer to a character */
int  var = 20;   /* variable declaration */
int  *ip;        /* pointer declaration */

ip = &var;  /* store address of var in pointer variable*/

NSLog(@"Address of var variable: %x\n", &var  );

NSLog(@"Address stored in ip variable: %x\n", ip );

NSLog(@"Value of *ip variable: %d\n", *ip );

Strings

- (NSString *)capitalizedString;
capitalize the string.

- (unichar)characterAtIndex:(NSUInteger)index;
get the character at a given index.

- (double)doubleValue;
Converts string value to the double value.

- (float)floatValue;
Converts to float value.

- (BOOL)hasPrefix:(NSString *)aString;
Checks if the string is started with another string.

- (BOOL)hasSuffix:(NSString *)aString;
Checks if the string is ended with another string.

- (id)initWithFormat:(NSString *)format ...;
Formats a string.

- (NSInteger)integerValue;
Converts string to NSInteger value.

- (BOOL)isEqualToString:(NSString *)aString;
Compares two strings.

- (NSUInteger)length;
Returns the number of characters in the String.

- (NSString *)lowercaseString;
Lowercase the String.

- (NSRange)rangeOfString:(NSString *)aString;
Searches a sub string.

- (NSString *)stringByAppendingFormat:(NSString *)format ...;
Appends to string with format.

- (NSString *)stringByTrimmingCharactersInSet:(NSCharacterSet *)set;
Trims characters from the string.

- (NSString *)substringFromIndex:(NSUInteger)anIndex ;
Gets the sub string from index.

Append sub string

NSMutableString *largeString;
largeString = [NSMutableString stringWithString: @"That is a string"];
NSLog (@"Original string = %@", largeString);
[largeString appendString: @" and this is a string too."];
NSLog (@"New string = %@", largeString);  

prefix and suffixes

NSString *myName = @"John Doe";
NSString *hisName = @"John Doe";
if ([myName isEqualToString: hisName])
{
NSLog (@"The two strings are equal using isEqualToString.");
}
BOOL flag;
flag = [myName hasPrefix: @"John"];
if (flag)
{
NSLog (@"The hasPrefix method returned YES.");
}  

Convert to uppercase and lowercase

NSString *testString = @"Greetings from another planet!";
NSString *targetString;
targetString = [testString uppercaseString];
NSLog (@"All uppercase = %@", targetString);
NSLog (@"**********");
targetString = [testString lowercaseString];
NSLog (@"All lowercase = %@", targetString);
NSLog (@"**********");
targetString = [testString capitalizedString];
NSLog (@"All capitalized strings = %@", targetString);
NSLog (@"**********");
NSLog (@"Original string = %@", testString);  

Delete part of a string

NSMutableString *largeString;
largeString = [NSMutableString stringWithString: @"That is a string"];
NSLog (@"Original string = %@", largeString);
[largeString deleteCharactersInRange: [largeString rangeOfString: @"is a "]];
NSLog (@"New string = %@", largeString);

Extracting a Substring to the End of a String

NSMutableString *largeString;
largeString = [NSMutableString stringWithString: @"That is a string"];
NSLog (@"Original string = %@", largeString);
NSString *newString;
newString = [largeString substringFromIndex: 5];
NSLog (@"New string = %@", newString);  

Extracting a Substring with Location and Length

NSMutableString *largeString;
largeString = [NSMutableString stringWithString: @"That is a string"];
NSLog (@"Original string = %@", largeString);
NSString *newString;
newString = [largeString substringWithRange: NSMakeRange(5, 4)];
NSLog (@"New string = %@", newString);  

Get the length of a string

NSString *myString = @"Hello, world!";
int counter;
counter = [myString length];
NSLog (@"String length = %i", counter);  

Insert a string

NSMutableString *largeString;
largeString = [NSMutableString stringWithString: @"That is a string"];
NSLog (@"Original string = %@", largeString);
[largeString insertString: @"was and still " atIndex: 5];
NSLog (@"New string = %@", largeString); 

Searching and Replacing Strings

NSMutableString *largeString;
largeString = [NSMutableString stringWithString: @"That is a string"];
NSLog (@"Original string = %@", largeString);
[largeString replaceCharactersInRange: NSMakeRange(5,2) withString: @"was not"];
NSLog (@"New string = %@", largeString);

Searching and Replacing Part of a String

NSMutableString *largeString;
largeString = [NSMutableString stringWithString: @"That is a string"];
NSLog (@"Original string = %@", largeString);
[largeString replaceCharactersInRange: [largeString rangeOfString: @"is"]  withString: @"was not"];
NSLog (@"New string = %@", largeString);

Searching for a Substring

NSRange myRange;
NSString *bigString = @"Learning to program can be fun!";
myRange = [bigString rangeOfString: @"can be"];
if (myRange.location == NSNotFound)
{
NSLog (@"Substring is not in %@", bigString);
}
else
{
NSLog (@"Substring found at location = %i", myRange.location);
NSLog (@"Substring length = %i", myRange.length);
}

Compare two Strings

NSString *myString1 = @"A";
NSString *myString2 = @"B";
NSString *myString3 = @"A";

BOOL isEqual = [myString1 isEqualToString:myString2];

Get a Range of String

[myString setString:@"ABCDEFGHIJKLMONPQRSTUVWXYZ"];

NSRange rangeToReplace = NSMakeRange(0, 4);
[myString replaceCharactersInRange:rangeToReplace withString:@"MORE"];

Structures

struct [structureName]
{
member definition;
member definition;
...
member definition;
} [one or more structure variables];


struct Books
{
NSString *title;
NSString *author;
NSString *subject;
int      id;
};

struct Books Book1;        /* Declare Book1 of type Book */

Book1.title = @"Objective-C Programming";
Book1.author = @"java2s.com"; 
Book1.subject = @"Objective-C Programming Tutorial";
Book1.id = 1;

Typedef

typedef unsigned char BYTE;

Lists the methods from NSNumber.

+ (NSNumber *)numberWithBool:(BOOL)value
Creates and returns an NSNumber object for a BOOL value.

+ (NSNumber *)numberWithChar:(char)value
Creates and returns an NSNumber object from a signed char value.

+ (NSNumber *)numberWithDouble:(double)value
Creates and returns an NSNumber object from a double value.

+ (NSNumber *)numberWithFloat:(float)value
Creates and returns an NSNumber object from a float value.

+ (NSNumber *)numberWithInt:(int)value
Creates and returns an NSNumber object from a signed int.

+ (NSNumber *)numberWithInteger:(NSInteger)value
Creates and returns an NSNumber object from an NSInteger.

- (BOOL)boolValue
Returns the value as a BOOL.

- (char)charValue
Returns the value as a char.

- (double)doubleValue
Returns the value as a double.

- (float)floatValue
Returns the value as a float.

- (NSInteger)integerValue
Returns the value as an NSInteger.

- (int)intValue
Returns the value as an int.

- (NSString *)stringValue
Returns the value as a human-readable string.

NSNumber *myNumber;
myNumber = [NSNumber numberWithFloat:3.47];
NSLog (@"The value in NSNumber = %@", myNumber);  

Convert Float NSNumber to String

float fNumber = 12;

NSString *floatToString = [NSString stringWithFormat:@"%f", fNumber];

NSLog(@"floatToString = %@", floatToString);

NSNumber *number = [NSNumber numberWithFloat:30];

NSString *numberToString = [number stringValue];

NSLog(@"numberToString = %@", numberToString);

Convert String to Number

NSString *aFloatValue = @"12.50";

float f = [aFloatValue floatValue];

float result = f * 2 + 45;

NSLog(@"f = %f and result = %f", f, result);

NSNumber *aFloatNumber = [NSNumber numberWithFloat:[aFloatValue floatValue]];

NSLog(@"aFloatNumber = %@", aFloatNumber);

Format a Number

NSNumber *numberToFormat = [NSNumber numberWithFloat:9.99];

NSLog(@"numberToFormat = %@", numberToFormat);

NSNumberFormatter *numberFormatter = [[NSNumberFormatter alloc] init];

numberFormatter.numberStyle = NSNumberFormatterCurrencyStyle;

NSLog(@"Formatted for currency: %@", [numberFormatter stringFromNumber:numberToFormat]);

numberFormatter.numberStyle = NSNumberFormatterSpellOutStyle;

NSLog(@"Formatted for spelling out: %@", [numberFormatter stringFromNumber:numberToFormat]);

we tried to cover as many as Objective-C data types, still we missed something, please let us know

Happy Coding 🙂