That's right, because cash is money now, bonds is money later. If inflation is high I'd rather have $100 now than $100 later.

Of course, real decisions are made on figures. The actual way of making this decision would be to compare the bond yield with the expected inflation. If expected inflation is higher than the bonds yields I'm going to sell my bonds for cash and so will a lot of people, so the bonds price will drop and the yields will raise until a point where they're attractive again.

But yes, it is hard.