I have code like this -
type StateTypes = State1 | State2;
class State1 {
static handleA (): StateTypes {
// Do Something
return State2;
}
static handleB (): StateTypes {
// Do Something
return State1;
}
}
class State2 {
static handleA (): StateTypes {
// Do Something
return State1;
}
static handleB (): StateTypes {
// Do Something
return State2;
}
}
let currentState: StateTypes = State1;
for (/* some Condition*/){
if(/* some Condition*/)
currentState = currentState.handleA();
else
currentState = currentState.handleB();
}
It works perfectly fine, however Typescript complains that it cannot find the static method handlaA() in class State1.
TS2339: Property 'handleA' does not exist on type 'StateTypes'. Property 'handleA' does not exist on type 'State1'.
type StateTypes = State1 | State2 means instance of State1 or State2.
What you want is: type StateTypes = typeof State1 | typeof State2. This refers to constructors instead of instances
It seems that return State1 does not return what you expect it to. You can test that out in a simpler example:
class State2 {
static handleB (): State1 {
return State1
}
}
class State1 {
static test (): void {
console.log("testing")
}
}
Here we hope to get a reference to State1
let currentState = State2.handleB()
currentState.test()
But the error is the same: Property 'test' does not exist on type 'State1'.
You might solve it by making the state an instance. Then you can get a reference to a different state. You can overwrite it with an instance of the new state.
type currentState = State1 | State2
class State2 {
getNewState (): State1 {
return new State1()
}
testMessage (): void {
console.log("state two")
}
}
class State1 {
getNewState (): State2 {
return new State2()
}
testMessage (): void {
console.log("state one")
}
}
let currentState = new State2()
// ask for the new state
currentState = currentState.getNewState()
currentState.testMessage()