子视图控制器大小问题

我有一个视图控制器,在导航栏中有一个分段控件,用于切换子视图控制器和父控制器。它工作得很好,但是我小时候的表视图大小不正确。它在底部被切断。

母VC:

import UIKit

class ShareTabViewController: UIViewController {

    let segementedControl = UISegmentedControl(items: ["Share", "Blog", "Progress"])

    override func viewDidLoad() {
        super.viewDidLoad()

        self.segementedControl.sizeToFit()
        self.segementedControl.tintColor = Constants.Colors.raPurple
        self.segementedControl.selectedSegmentIndex = 0
        self.segementedControl.addTarget(self, action: #selector(selectionChanged(_:)), for: .valueChanged)
        self.navigationItem.titleView = self.segementedControl

        let shareVC = ShareTableViewController()
        self.view.addSubview(shareVC.view)
        self.addChild(shareVC)
        shareVC.didMove(toParent: self)
    }

    @objc func selectionChanged(_ sender: UISegmentedControl) {
        for subview in self.view.subviews {
            subview.removeFromSuperview()
        }

        for childVC in self.children {
            childVC.removeFromParent()
        }

        switch sender.selectedSegmentIndex {
        case 0:
            let shareVC = ShareTableViewController()
            self.view.addSubview(shareVC.view)
            self.addChild(shareVC)
        case 1:
            let blogVC = BlogViewController()
            self.view.addSubview(blogVC.view)
            self.addChild(blogVC)
        case 2:
            let progressVC = ProgressViewController()
             self.view.addSubview(progressVC.view)
            self.addChild(progressVC)
        default:
            print("default")
        }
    }
}