@interface Human : NSObject

// Define properties and methods

@end

#import "Human.h"

@interface Human ()
// Define private properties and methods
@end

@implementation Human {
// Define private instance variables
}

// Provide method implementation code

@end

Human * anObject = [[Human alloc] init];

// Returns nothing and has no arguments
- (void)foo;

// Returns an NSString object and takes one argument of type NSObject
- (NSString *)fooWithArgument:(NSObject *)bar;

// Takes two arguments one of type NSObject and a second one of type NSString
- (void)fooWithArgument:(NSObject *)bar andArgument:(NSString *)baz;

// Defines a class method (note the + sign)
+ (void)aClassMethod;

- (NSString *)fooWithArgument:(NSObject *)bar{
    // Do something here
    return retValue;
}

[anObject someMethod];
[anObject someMethodWithArg1:arg1 andArg2:arg2];

@property (attribute1, attribute2) NSString *aProperty;

[anObject aProperty];

// Alternative
anObject.aProperty

#define MAX_NUMBER_OF_ITEMS 10

NSString *const kMyName = @"Clark";

static NSString * const kMyName = @"Clark";

// .h file
extern NSString * const kMyName;

// .m file
NSString * const kMyName = @"Clark";

if (someCondition) {
    // Execute if the condition is true
} else if (someOtherCondition) {
    // Execute if the other condition is true
} else {
    // Execute if the none of the above conditions are true
}

someCondition ? @"True" : @"False";

for (int i = 0; i < totalCount; i++) {
    // Do something here
}

while (someCondition) {
   // Do something here
}

do {
    // Do something here
} while (someCondition);

switch (aLabel)
{
    case kLabelA:
        // Execute this if matched
        break;

     case kLabelB:
        // Execute this if matched
        break;

     default:
        // Execute this if matched
        break;
}

// MyTableViewController.h

@interface MyTableViewController : UIViewController <UITableViewDelegate, UITableViewDataSource>

@end

// MyTableViewController.m

[tableView setDelegate:self];

@end

// Superman.h
#import <Foundation/Foundation.h>

@protocol SupermanDelegate <NSObject>

- (void)dodgeBullet;
- (void)seeThroughThings;
- (void)fly;

@optional
- (void)eat;

@end

@interface Superman : NSObject

// Create a property for the delegate reference
@property (nonatomic, weak) id <SupermanDelegate> delegate;

// Define other methods and properties

@end

// Superman.m

[self setDelegate:anObject];

// Superman.m

[self.delegate fly];

if ([self.delegate respondsToSelector:@selector(eat)]) {
  [self.delegate eat];
}

typedef returnType (^TypeName)(parameterTypes);
TypeName blockName = ^returnType(parameters) {...};

NSString *firstName = @"Clark";
NSString *lastName = @"Kent";
NSString *fullName = [NSString stringWithFormat:  @"My full name is %@ %@",  firstName, lastName];

// Create an array
NSMutableArray *anArray = [@[@"Clark Kent", @"Lois Lane"] mutableCopy];

// Add new items
[anArray addObject:@"Lex Luthor"];

// Find array length
NSLog(@"Array has %d items", [anArray count]);

// Iterate over array items
for (NSString *person in anArray) {
 NSLog(@"Person: %@", person);
}

// Access item with index
NSString *superman = anArray[0];

// Remove Object @"Clark Kent"
[anArray removeObject:@"Clark Kent"];

// Remove the first Object
[anArray removeObjectAtIndex:0];

// Create a dictionary
NSMutableDictionary *person = [@{
                             @"firstname" : @"Clark",
                             @"lastname" : @"Kent",
                             @"age" : [NSNumber numberWithInt:35]
                             } mutableCopy];

// Access values
NSLog(@"Superman's first name is %@", person[@"firstname"]);
// or
NSLog(@"Superman's first name is %@", [person objectForKey:@"firstname"]);

// Find number of items in dictionary
[person count];

// Add an object to a dictionary
[person setObject:@"job" forKey:@"teacher"];

// Remove an object to a dictionary
[person removeObjectForKey:@"firstname"];

NSString *string = @"This is a string.";

NSNumber *number = @126;      // int          : Equal to [NSNumber numberWithInt:126];
NSNumber *number = @126u;     // unsigned int : Equal to [NSNumber numberWithUnsignedInt:126u];
NSNumber *number = @126l;     // long         : Equal to [NSNumber numberWithLong:126l];
NSNumber *number = @126.544f; // float        : Equal to [NSNumber numberWithFloat:126.544f]
NSNumber *number = @126.544;  // double       : Equal to [NSNumber numberWithDouble:126.544]
NSNumber *number = @YES;      // bool         : Equal to [NSNumber numberWithBool:YES]

NSArray *array = @[object1,object2,object3]; // Creating NSArray
Object *object2 = array[1]; // Accessing NSArray
mutableArray[1] = newObject; // Adding to NSMutableArray

NSDictionary *dictionary = @{ @"key1" : object1, @"key2" : object2, @"key3" : object3 }; // Creating NSDictionary
Object *object2 = dictionary[@"key2"]; // Accessing NSDictionary
mutableDictionary[@"name"] = @"Henry"; // Adding to NSMutableDictionary

typedef NS_ENUM(NSInteger, UIButtonType) {
   UIButtonTypeCustom,
   UIButtonTypeSystem,
   UIButtonTypeDetailDisclosure,
   UIButtonTypeInfoLight,
   UIButtonTypeInfoDark,
   UIButtonTypeContactAdd,
   UIButtonTypeRoundedRect
};

typedef NS_ENUM(NSInteger, UIButtonType) {
   UIButtonTypeCustom = 0,
   UIButtonTypeSystem = 1,
   UIButtonTypeDetailDisclosure = 2,
   UIButtonTypeInfoLight = 3,
   UIButtonTypeInfoDark = 4,
   UIButtonTypeContactAdd = 5,
   UIButtonTypeRoundedRect = 6
};

UIButton *button = [UIButton buttonWithType:UIButtonTypeInfoLight];

UIButtonType myButtonType = UIButtonTypeCustom;
UIButton *myButton = [UIButton buttonWithType:myButtonType];

UIButtonType myButtonType = UIButtonTypeRoundedRect;

// Bad, will give you a warning and might even crash
NSLog(@"%@", myButtonType);

// Good, will properly print the value as an integer
NSLog(@"%d", myButtonType);