将 UIImageView 设为：

myImageView.image = nil 

UIImageView 。在调用函数返回时加载图像？是你的 UIImageView 被声明和/或在你的主要函数的其他地方使用吗？

is the correct way to clear an UIImageView. Are you loading the image when your calling function returns? Is your UIImageView being declared, and/or used elsewhere in your main function?