Effective Objective-C 2.0 编写高质量iOS与OS X代码的52个有效方法（一）

NSNumber *number = [NSNumber numberWithInt:1];
//字面量写法：
NSNumber *number = @1;
NSNumber *doubleNumber = @3.14159;
NSNumber *boolNumber = @yes;
NSNumber *charNumber = @‘a’;

int x = 5;
float y = 6.23f;
NSNumber *expressNumber = @(x * y);

NSArray *animals = [NSArray arrayWithObjects:@“cat”, @“dog”, @“mouse”, @“badger”, nil];
// 使用字面量：
NSArray *animals = @[@“cat”, @“dog”, @“mouse”, @“badger”];

NSArray *arr1 = [NSArray arrayWithObjects:object1, object2, object3, nil];
NSArray *arr2 = @[object1, object2, object3];

NSDictionary *person = [NSDictionary dictionaryWithObjectAndKeys:@“matt”,@“first name”，@“galloway”, @“lastName”,nil];
// 使用字面量：
NSDictionary *person = @{@“first name”:@“matt”, @“lastName”:@“galloway”};

NSString *lastName = [person objectForKey:@“lastname”];
NSString *lastName = person[@“lastname”];

typedef NS_ENUM(NSUInteger, EOCConnectionState) {
     EOCConnectionStateDisconnected,
     EOCConnectionStateDisconnected,
     EOCConnectionStateDisconnected
};
typedef NS_OPTIONS(NSUInteger, EOCPermittedDirection) {
     EOCCPermittedDirectionUp = 1 << 0,
     EOCCPermittedDirectionDown = 1 << 1,
     EOCCPermittedDirectionLeft = 1 << 2,
     EOCCPermittedDirectionRight = 1 << 3,
};

enum EOCConnectionState connectionState : NSInteger { // };