Swift新手遇Xcode报错：调用时缺少参数标签'at:'

Hey there, let's break down why you're seeing this error and how to fix it quickly for your Swift app.

What's Causing the Error? #

The core issue here is that Swift's standard Array type doesn't have a remove(_:) method that accepts an element directly. The remove method you’re trying to use requires you to specify an element’s position with the at: argument label (like remove(at: someIndex)), but you’re passing in the element itself instead of its index in the array.

Solution 1: Find the Element's Index First, Then Remove It #

If you’re certain the element exists in your comments or imageFile arrays, you can first locate its index with firstIndex(of:), then delete it safely. We’ll also replace those risky as! force-unwraps with optional binding to avoid crashes:

// Remove the target comment
if let targetComment = post["message"] as? String, 
   let commentIndex = self.comments.firstIndex(of: targetComment) {
    self.comments.remove(at: commentIndex)
}

// Remove the target image file
if let targetFile = post["imageFile"] as? PFFile, 
   let fileIndex = self.imageFile.firstIndex(of: targetFile) {
    self.imageFile.remove(at: fileIndex)
}

Note: firstIndex(of:) only finds the first occurrence of the element. If your array has duplicates, this method will only delete the first matching entry.

Solution 2: Use filter to Create a New Array Without the Target Element #

If you want to delete all instances of the element (or avoid dealing with indexes entirely), use filter to generate a new array that excludes the element you want to remove:

// Remove all matching comments
if let commentToRemove = post["message"] as? String {
    self.comments = self.comments.filter { $0 != commentToRemove }
}

// Remove all matching image files
if let fileToRemove = post["imageFile"] as? PFFile {
    self.imageFile = self.imageFile.filter { $0 != fileToRemove }
}

This approach is safer because it eliminates the risk of index out-of-bounds errors, and it’s cleaner if you need to remove every occurrence of the target element.

Quick Pro Tip: Ditch Force Unwraps! #

Your original code uses as!, which will crash your app if post["message"] or post["imageFile"] is missing or the wrong type. Always use as? with optional binding (like in the examples above) to handle these edge cases gracefully.

内容的提问来源于stack exchange，提问作者Daniel.P