Modern Objective-C syntax

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随着Swift的加入，OC在不也在不断向着新的编程方式靠拢，虽然OC是我很喜欢的一门很优雅的语言，但是毕竟编程讲究的是效率，时代的大浪下，OC的很多写法也顺应大潮做出了一些相应的改变。
下面我们来看一下都有哪些地方现代化OC语法做出的改变。

1. 将一些单纯的方法转换为属性

- (BOOL)isGrade;
@property (NS_NONATOMIC_IOSONLY, getter=isGrade, readonly) BOOL grade;

2. 将一些中括号调用变为属性调用

2.1. get方法调用的修改

[[NSBundle mainBundle] infoDictionary]
[NSBundle mainBundle].infoDictionary

[[UIScreen mainScreen] bounds]
[UIScreen mainScreen].bounds

[[[UIApplication sharedApplication] delegate] window]
[UIApplication sharedApplication].delegate.window

类似的还有length、count等等

2.2. set方法调用的修改

将setImage这种类似的setter方法转换为.语法的setter赋值

image = [[UIImageView alloc] init];
[image setImage:[UIImage imageNamed:@"name.png"]];
image.image = [UIImage imageNamed:@"name.png"];

[btn setBackgroundColor:[UIColor redColor]];
btn.backgroundColor = [UIColor redColor];

3.将初始化 init 方法的返回值从 id 转换为转换为 instancetype

4.枚举宏定义的改变

将enum修改为NS_ENUM将枚举的后置修改为前置

Old Version

typedef enum { 
  EnumType, 
  EnumTypeA, 
  EnumTypeB 
} Type;

Modern Version:

typedef NS_ENUM (NSUInteger Type) { 
  EnumType, 
  EnumTypeA, 
  EnumTypeB 
};

6.字典和数组的一些赋值和取值的方式

6.1 字典

[dict setObject:value forKey:key];
dict[key] = value;
id value = [dict objectForKey: key]
id value = dict[key]

6.2 数组

[array objectAtIndex:index]
array[index]

7. 变量

@implementation Manager {
    UIButton *loginButton;
}

@interface HHMyClass ()
@property (nonatomic) UIButton *loginButton;
@end
@implementation HHMyClass
...
@end

8. 数组和字典的初始化

NSNumber *number = [NSNumber numberWithInteger:7];
NSNumber *modernNumber = @(7); // or @7

NSArray *array = [NSArray arrayWithObjects:number, modernNumber, nil];
NSArray *modernArray = @[number, modernNumber];

NSDictionary *dictionary = [NSDictionary dictionaryWithObjectsAndKeys:number, @"number"];
NSDictionary *modernDictionary = @{@"number" : number};