What is the proper way of disciplining a child?

My mother got really angry over her nephew's wife because she beat her first child which is just 1 yr. old. My mother is very close to this child. That is why it hurts for her to see the child being beaten. The reason behind this was about a toy which was bought by her mother. The child throw it away for and it was destroyed. Her mom got mad because the toy are expensive. Ever since, the child was already used to beatings. However, my mom argues that they shouldn't discipline their child in that way. Not like that. And money is money. It can be earned again. But for child, it can't be replaced. What is your view about this mylotters?