Left-align image and center text on UIButton

This solution works with Swift 3 and respects original content and image edge insets while keeping the title label always centered in the available space, which makes much easier adjusting margins.

It overrides titleRect(forContentRect:) method and returns the correct frame:

@IBDesignable
class LeftAlignedIconButton: UIButton {
    override func titleRect(forContentRect contentRect: CGRect) -> CGRect {
        let titleRect = super.titleRect(forContentRect: contentRect)
        let imageSize = currentImage?.size ?? .zero
        let availableWidth = contentRect.width - imageEdgeInsets.right - imageSize.width - titleRect.width
        return titleRect.offsetBy(dx: round(availableWidth / 2), dy: 0)
    }
}

The following insets:

Would result in this:

Deprecated previous answer

This works in most scenarios, but some layouts cause layoutSubviews to recursively call itself in an endless loop, so use with caution.

@IBDesignable
class LeftAlignedIconButton: UIButton {
    override func layoutSubviews() {
        super.layoutSubviews()
        contentHorizontalAlignment = .left
        let availableSpace = UIEdgeInsetsInsetRect(bounds, contentEdgeInsets)
        let availableWidth = availableSpace.width - imageEdgeInsets.right - (imageView?.frame.width ?? 0) - (titleLabel?.frame.width ?? 0)
        titleEdgeInsets = UIEdgeInsets(top: 0, left: availableWidth / 2, bottom: 0, right: 0)
    }
}

This code would do the same but aligning the icon to the right edge:

@IBDesignable
class RightAlignedIconButton: UIButton {
    override func layoutSubviews() {
        super.layoutSubviews()
        semanticContentAttribute = .forceRightToLeft
        contentHorizontalAlignment = .right
        let availableSpace = UIEdgeInsetsInsetRect(bounds, contentEdgeInsets)
        let availableWidth = availableSpace.width - imageEdgeInsets.left - (imageView?.frame.width ?? 0) - (titleLabel?.frame.width ?? 0)
        titleEdgeInsets = UIEdgeInsets(top: 0, left: 0, bottom: 0, right: availableWidth / 2)
    }
}

The right allignment version uses semanticContentAttribute so it requires iOS 9+.