What are borderRect, editingRect, placeholderRect, textRect in UITextField?

Question

From the answer previously posted, I understand that editingRect is the rectangle shown when the text is being edited, and textRect is the one shown when the text is not being edited. But I don't know where exactly placeholderRect and borderRect are displayed in a UITextField control. I assumed the borderRect would be the same as the frame rect of UITextField because of the word 'border' in it, but after doing this:

override func borderRect(forBounds bounds: CGRect) -> CGRect {
    let rect = bounds
    rect.size.height = 150 //the height of my UITextField currently is 100
    return rect
}

I realized it was not. So what are placeholderRect and borderRect, and where are they located in UITextField?

Answer 1

borderRect refers to the frame of the border (which will exist for a text field if borderStyle != .none), and placeholderRect refers to the frame of the placeholder text - the text that appears when text is empty.

Here is a little sample that you can paste into a playground, that shows where all the rects are. I returned different quarters the bounds rect for each of the text field rects.

class TextFieldWithDifferentRects: UITextField {
    override func textRect(forBounds bounds: CGRect) -> CGRect {
        // top left
        CGRect(x: bounds.minX, y: bounds.minY, width: bounds.width / 2, height: bounds.height / 2)
    }
    
    override func placeholderRect(forBounds bounds: CGRect) -> CGRect {
        // top right
        CGRect(x: bounds.midX, y: bounds.minY, width: bounds.width / 2, height: bounds.height / 2)
    }
    
    override func borderRect(forBounds bounds: CGRect) -> CGRect {
        // bottom left
        CGRect(x: bounds.minX, y: bounds.midY, width: bounds.width / 2, height: bounds.height / 2)
    }
    
    override func editingRect(forBounds bounds: CGRect) -> CGRect {
        // bottom right
        CGRect(x: bounds.midX, y: bounds.midY, width: bounds.width / 2, height: bounds.height / 2)
    }
}

let view = TextFieldWithDifferentRects(frame: CGRect(x: 0, y: 0, width: 200, height: 200))
view.backgroundColor = .white // make the placeholder text more visible
view.borderStyle = .line
view.placeholder = "a" // use the playground quick view button here
view.text = "b" // and here

// by selecting everything, we kick the text field into edit mode, to show the editingRect
view.selectAll(nil) // and lastly here

Output: