多线程的使用

一、Thread

import UIKit

class ViewController: UIViewController {
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        let operation = BlockOperation(block: { [weak self] in
            self?.downloadImage()
            return
            })
        
        //创建一个NSOperationQueue实例并添加operation
        let queue = OperationQueue()
        queue.addOperation(operation)
    }
    
    //定义一个下载图片的方法，线程调用
    func downloadImage(){
        let imageUrl = "http://hangge.com/blog/images/logo.png"
        let data = try! Data(contentsOf: URL(string: imageUrl)!)
        print("该方法被线程2调用")
        print(data.count)
    }
    
    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }
}