Function used before being declared?

Question

class myClass {
public:
myClass(string nm) {
setName(nm);
}
void setName(string x) {
name = x;
}
string getName() {
return name;
}
private:
string name;
};

int main() {
myClass ob1("David");
myClass ob2("Amy");
cout << ob1.getName();
}
//Outputs "David"

why don't we get an error here, because the function setName is used before being declared.