Lesson 4 Recap - cogeorg/teaching GitHub Wiki

In this lesson, you mainly practice concepts that have been introduced in one of the previous lessons.

Chapter 1 + 2: introduces the payable modifier
- allows contracts to receive ether through a function call
```
function buySomething() external payable {
    // do something
}
```
- there needs to be a special function for the owner of the contract to withdraw the money
Chapter 3: practice
Chapter 4: explains why a Solidity random number generator in insecure
- a hostile user could decide to only publish/mine a transaction when she wins a random game
Chapter 5: practice
Chapter 6 + 7: refactoring code by outsourcing to modifiers
Chapter 8 + 9 + 10: practice
Chapter 11: explains if/else syntax

if (<condition>){
    // do something
} else if (<other condition>){
    // do something else
} else {
    // do something completely else
}