先把控件addSubviews上 然後再拉約束,如下
let imageView = UIImageView.init()
imageView.image = UIImage(named: "comment_head")
backView.addSubview(imageView)
imageView.snp_makeConstraints { (make) in
make.top.equalTo(backView).offset(10)
make.left.equalTo(backView).offset(10)
make.width.equalTo(36)
make.height.equalTo(36)
}