Swift Day18 OC 和 Swift 混编

1. Swift调用OC代码

• 创建OC下的 LSPerson 类

@interface LSPerson : NSObject

@property (nonatomic, assign) int age;
@property (nonatomic, strong) NSString *name;

- (instancetype)initWithAge:(int)age name:(NSString*)name;

@end

• 首次创建OC代码时，会自动创建 OC-Bridging-Header.h 文件，这个文件主要用于声明Swift中要用到的OC文件

//  OC-Bridging-Header.h
//
//  Use this file to import your target's public headers that you would like to expose to Swift.
//

#import "LSPerson.h"

• Swift中调用LSPerson

class ViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        let person: LSPerson = LSPerson(age: 10, name: "carrot");
        person.age = 20
        print(person.age)   // 输出:20
        print(person.name)  // 输出:carrot
    }
}

2. OC调用Swift代码

• 需要被OC调用的Swift代码有两个条件：①继承自NSObject ②使用@objcMembers 将成员和方法暴露出去

@objcMembers class Car: NSObject {
    var price = 100.5
    var owner = "lsp"
    init(price: Double, owner: String) {
        self.price = price
        self.owner = owner
    }
}

• 在需要调用Swift的OC代码处引入 #import "OC-Swift.h"，这个文件默认存在

#import "LSPerson.h"
#import "OC-Swift.h"

@implementation LSPerson
-(void)callSwiftClass {
    Car *car = [[Car alloc] initWithPrice:300.5 owner:@"carrot"];
    NSLog(@"%@ %f %@",car, car.price, car.owner); // 输出：<OC.Car: 0x600001031b00> 300.500000 carrot
}

@end

3. Swift 中字符串的基本用法

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4. String 和 Substring 的关系

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