class RTFather {
// Father init
RTFather() {
print("Father init");
}

// flutter: Father design init
RTFather.design() {
print("Father design init");
}
}

class RTSon extends RTFather {
RTSon() {
// flutter: Father init
// flutter: Son init

print("Son init");

}

// flutter: Father init
// flutter: Son design init

RTSon.design() {
print("Son design init");
}
}

////////
class RTFather {
// Father init
RTFather(String a) {
print("Father init");
}

// flutter: Father design init
RTFather.design() {
print("Father design init");
}
}

class RTSon extends RTFather {
RTSon() : super('') {
// flutter: Father init
// flutter: Son init

print("Son init");

}

// flutter: Father init
// flutter: Son design init

RTSon.design() : super(''){
print("Son design init");
}
}