修改main.m文件

#import <Foundation/Foundation.h>
#import "Root.h"

int main(int argc,const char * argv[])
{
    @autoreleasepool
    {
        Root *rt = [[Root alloc] init];
        [rt desc];
    }
    return 0;
}

#import <Foundation/Foundation.h>

//Objective-c 的头文件如果需要引用Swift的类，则可以使用下面这种方式
@class Person;

@interface Root : NSObject

-(Person *)returnPerson;
-(void)desc;

@end

#import "Root.h"

//Objective-c调用Swift
//需要导入固定的头文件，此头文件项目里面找不到，但却是存在。并且会自动把Swift类转换成OC的类，在里面能找到
//格式为 #ProductName#-Swift.h
#import <OC_Swift-Swift.h>


@implementation Root

-(void)desc
{
    Person *ps = [[Person alloc] initWithName:@"Rose"];
    ps.name = @"Jack";
    [ps desc];
}

-(Person *)returnPerson
{
    Person *ps = [[Person alloc] initWithName:@"Tom"];
    return ps;
}

@end

import Foundation

//如果此类需要被OC的类来调用，一定要继承自NSObject
class Person : NSObject
{
    var name: String
    {
        willSet
        {
            NSLog("将要把名字设置为:" + name)
        }
    }
    override init()
    {
        self.name = ""
    }
    init(name: String)
    {
        self.name = name
    }
    func desc()
    {
        print("这是一个Swift的类，name: " + self.name)
    }
}