无法在局部函数swift中附加到全局变量

Question

这是我的视图控制器类

import UIKit

class ViewController: UIViewController, UITableViewDataSource, UITableViewDelegate {

    @IBOutlet weak var contact_Table: UITableView!

    var  contacts : [Contact] = [Contact]()
    var conj : [Contact] = [Contact]()

    override func viewDidLoad() {
        super.viewDidLoad()

        self.populate()
        // Do any additional setup after loading the view, typically from a nib.
    }

func populate()
    {

        let urlstring = "https://api.myjson.com/bins/25976"

        let url = NSURL(string : urlstring)

        let task = NSURLSession.sharedSession().dataTaskWithURL(url!) { (data,response, error) -> Void in
            dispatch_async(dispatch_get_main_queue(), {

                var jsonerror : NSError?

                let json = NSJSONSerialization.JSONObjectWithData(data, options: nil, error: &jsonerror)
                    as! NSDictionary

                if let  list_of_doctors = json["doctors"] as? NSArray{

                    let no_of_contacts = list_of_doctors.count-1
                    for index in 0...no_of_contacts
                    {
                        if let single_contact = list_of_doctors[index] as? NSDictionary{

                            let first_name = single_contact["first_name"] as? String               

                            let last_name=single_contact["last_name"] as? Strin                            

                            let password = single_contact["password"] as? String

                            var contactjson = Contact(online: "online_green_dot.jpeg", type: "iamge_nurse.png", name: first_name!, workplace_image: "hospital.png", designation: password!, workplace: last_name!)
                          contacts.append(contactjson)

                        }
                    }
                }
         })
    }
   task.resume()

即使联系人是一个局部变量，我也无法使用contacts.append()附加数据它要求我使用self.contacts.append()

Answer 1

编译器强制您显式调用self，因为self 被强烈 捕获在闭包中（由contacts 隐式捕获）。所以你可以清楚地看到这个调用是对self的隐式引用。这也意味着您应该考虑在捕获列表中将self 设为weak 或unowned 引用：

// replace weak with unowned if self is always there/ not nil
let task = NSURLSession.sharedSession().dataTaskWithURL(url!) { [weak self] (data,response, error) -> Void in
            dispatch_async(dispatch_get_main_queue(), {

请注意，数组会在 0.85 秒后异步更新（至少对我而言）。因此，您应该在闭包中制作更新代码（用于表格视图），以确保 contacts 数组已更新。