Note that programs written in Objective-C retain their class declarations whencompiled into Mach-O binaries. Such class declarations include the name and type of:
Note that this names could be obfuscated to make the reversing of the binary more difficult.
Classes, Methods & Objects
Interface, Properties & Methods
// Declare the interface of the class
@interface MyVehicle : NSObject
// Declare the properties
@property NSString *vehicleType;
@property int numberOfWheels;
// Declare the methods
- (void)startEngine;
- (void)addWheels:(int)value;
@end
Class
@implementation MyVehicle : NSObject
// No need to indicate the properties, only define methods
- (void)startEngine {
NSLog(@"Engine started");
}
- (void)addWheels:(int)value {
self.numberOfWheels += value;
}
@end
Object & Call Method
To create an instance of a class the alloc method is called which allocate memory for each property and zero those allocations. Then init is called, which initilize the properties to the required values.
// Something like this:
MyVehicle *newVehicle = [[MyVehicle alloc] init];
// Which is usually expressed as:
MyVehicle *newVehicle = [MyVehicle new];
// To call a method
// [myClassInstance nameOfTheMethodFirstParam:param1 secondParam:param2]
[newVehicle addWheels:4];
Class Methods
Class methods are defined with the plus sign (+) not the hyphen (-) that is used with instance methods. Like the NSString class method stringWithString:
+ (id)stringWithString:(NSString *)aString;
Setter & Getter
To set & get properties, you could do it with a dot notation or like if you were calling a method:
// Set
newVehicle.numberOfWheels = 2;
[newVehicle setNumberOfWheels:3];
// Get
NSLog(@"Number of wheels: %i", newVehicle.numberOfWheels);
NSLog(@"Number of wheels: %i", [newVehicle numberOfWheels]);
Instance Variables
Alternatively to setter & getter methods you can use instance variables. These variables have the same name as the properties but starting with a "_":
Protocols are set of method declarations (without properties). A class that implements a protocol implement the declared methods.
There are 2 types of methods: mandatory and optional. By default a method is mandatory (but you can also indicate it with a @required tag). To indicate that a method is optional use @optional.
Basic classes are immutable, so to append a string to an existing one a new NSString needs to be created.
NSString *bookDescription = [NSString stringWithFormat:@"%@ by %@ was published in %@", bookTitle, bookAuthor, bookPublicationYear];
Or you could also use a mutable string class:
NSMutableString *mutableString = [NSMutableString stringWithString:@"The book "];
[mutableString appendString:bookTitle];
[mutableString appendString:@" was written by "];
[mutableString appendString:bookAuthor];
[mutableString appendString:@" and published in "];
[mutableString appendString:bookPublicationYear];
Number
// character literals.
NSNumber *theLetterZ = @'Z'; // equivalent to [NSNumber numberWithChar:'Z']
// integral literals.
NSNumber *fortyTwo = @42; // equivalent to [NSNumber numberWithInt:42]
NSNumber *fortyTwoUnsigned = @42U; // equivalent to [NSNumber numberWithUnsignedInt:42U]
NSNumber *fortyTwoLong = @42L; // equivalent to [NSNumber numberWithLong:42L]
NSNumber *fortyTwoLongLong = @42LL; // equivalent to [NSNumber numberWithLongLong:42LL]
// floating point literals.
NSNumber *piFloat = @3.141592654F; // equivalent to [NSNumber numberWithFloat:3.141592654F]
NSNumber *piDouble = @3.1415926535; // equivalent to [NSNumber numberWithDouble:3.1415926535]
// BOOL literals.
NSNumber *yesNumber = @YES; // equivalent to [NSNumber numberWithBool:YES]
NSNumber *noNumber = @NO; // equivalent to [NSNumber numberWithBool:NO]
Blocks are functions that behaves as objects so they can be passed to functions or stored in arrays or dictionaries. Also, they can represent a value if they are given values so it's similar to lambdas.
returnType (^blockName)(argumentType1, argumentType2, ...) = ^(argumentType1 param1, argumentType2 param2, ...){
//Perform operations here
};
// For example
int (^suma)(int, int) = ^(int a, int b){
return a+b;
};
NSLog(@"3+4 = %d", suma(3,4));
It's also possible to define a block type to be used as a parameter in functions:
// Define the block type
typedef void (^callbackLogger)(void);
// Create a bloack with the block type
callbackLogger myLogger = ^{
NSLog(@"%@", @"This is my block");
};
// Use it inside a function as a param
void genericLogger(callbackLogger blockParam) {
NSLog(@"%@", @"This is my function");
blockParam();
}
genericLogger(myLogger);
// Call it inline
genericLogger(^{
NSLog(@"%@", @"This is my second block");
});
Files
// Manager to manage files
NSFileManager *fileManager = [NSFileManager defaultManager];
// Check if file exists:
if ([fileManager fileExistsAtPath:@"/path/to/file.txt" ] == YES) {
NSLog (@"File exists");
}
// copy files
if ([fileManager copyItemAtPath: @"/path/to/file1.txt" toPath: @"/path/to/file2.txt" error:nil] == YES) {
NSLog (@"Copy successful");
}
// Check if the content of 2 files match
if ([fileManager contentsEqualAtPath:@"/path/to/file1.txt" andPath:@"/path/to/file2.txt"] == YES) {
NSLog (@"File contents match");
}
// Delete file
if ([fileManager removeItemAtPath:@"/path/to/file1.txt" error:nil]) {
NSLog(@"Removed successfully");
}
It's also possible to manage files using NSURL objects instead of NSString objects. The method names are similar, but with URL instead of Path.
Most basic classes has a method writeToFile:<path> atomically:<YES> encoding:<encoding> error:nil defined that allows them to be directly be written to a file:
