Swift 4中如何按列值对UITableView进行排序？

API 探路者

2026-5-15

Fixing the Sorting Issue in Your Bitcoin Price App

Hey Augusto, I spot the exact issue with your sorting code right away—let's break it down and get it working!

The Root Cause

In Swift, the sorted(by:) method is non-mutating: it doesn't modify the original array you call it on. Instead, it creates and returns a brand new array with elements sorted to your specifications.

In your current code, you're running self.ticker.sorted(by: { $0.change > $1.change }) but never assigning that sorted new array back to self.ticker. Your original array stays unchanged, so the table view has no reason to look different after reloading data.

The Simple Fix

All you need to do is assign the sorted result back to your ticker variable. Here's the corrected tap handler:

@objc func tapChangeFunction(sender: UITapGestureRecognizer) {
    // Assign the sorted array back to the original variable
    self.ticker = self.ticker.sorted(by: { $0.change > $1.change })
    DispatchQueue.main.async {
        self.table.reloadData()
    }
}

Bonus: Add Toggleable Sort Direction

If you want users to switch between ascending and descending order when tapping the header multiple times, add a small state variable to track the current sort direction:

// Add this property to your view controller
private var isChangeSortDescending = true

@objc func tapChangeFunction(sender: UITapGestureRecognizer) {
    // Sort based on the current direction
    self.ticker = self.ticker.sorted(by: {
        if isChangeSortDescending {
            return $0.change > $1.change
        } else {
            return $0.change < $1.change
        }
    })
    // Flip the direction for the next tap
    isChangeSortDescending.toggle()
    
    DispatchQueue.main.async {
        self.table.reloadData()
    }
}