CodeToLive

Objective-C Syntax

Objective-C's syntax is unique, blending C with Smalltalk-style message passing. Understanding its syntax is crucial for writing effective Objective-C code.

Message Passing Syntax

// Basic message passing
[receiver message];

// With arguments
[receiver messageWithArgument:arg1 andSecondArgument:arg2];

// Nested messages
NSString *result = [[object getFormatter] formatValue:value];
            

Method Declarations

// Instance method (- prefix)
- (returnType)methodName;
- (returnType)methodNameWithParameter:(parameterType)parameterName;

// Class method (+ prefix)
+ (returnType)classNameMethod;

// Example with multiple parameters
- (void)setName:(NSString *)name age:(NSInteger)age;
            

Data Types

Objective-C uses C's primitive types along with its own object types:

• int, float, double - Primitive numeric types
• BOOL - Boolean (YES/NO)
• id - Generic object pointer
• NSInteger, NSUInteger - Platform-specific integers
• CGFloat - Floating-point type for graphics
• NSString, NSNumber, NSArray - Foundation objects

String Syntax

// NSString literals (with @ prefix)
NSString *greeting = @"Hello, World!";

// String formatting
NSString *formatted = [NSString stringWithFormat:@"Count: %d, Price: %.2f", count, price];

// Mutable strings
NSMutableString *mutableString = [NSMutableString stringWithString:@"Hello"];
[mutableString appendString:@" World!"];
            

Control Structures

// If-else
if (condition) {
    // code
} else if (anotherCondition) {
    // code
} else {
    // code
}

// Fast enumeration (for-in)
for (id object in collection) {
    // code
}

// Traditional for loop
for (int i = 0; i < 10; i++) {
    // code
}

// While loop
while (condition) {
    // code
}

// Do-while
do {
    // code
} while (condition);
            

Blocks Syntax

Objective-C blocks are similar to lambdas or closures in other languages:

// Simple block
void (^simpleBlock)(void) = ^{
    NSLog(@"This is a block");
};
simpleBlock();

// Block with parameters and return value
double (^multiplyTwoValues)(double, double) = ^(double first, double second) {
    return first * second;
};
double result = multiplyTwoValues(2.5, 4.0);

// Using blocks with methods
[array enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
    NSLog(@"Object at index %lu: %@", (unsigned long)idx, obj);
}];
            

Selector Syntax

Selectors are used to represent method names:

// Creating a selector
SEL mySelector = @selector(methodName:withParameter:);

// Performing selectors
if ([object respondsToSelector:mySelector]) {
    [object performSelector:mySelector withObject:param1 withObject:param2];
}

// Using in target-action pattern
[button addTarget:self 
           action:@selector(buttonPressed:)
 forControlEvents:UIControlEventTouchUpInside];