I am playing around with UnionTypes in TS and I thought that I could create a valid scenario where they could be used, but I do not understand why this is breaking with the error of:
Argument of type '{ name: string; }' is not assignable to parameter of type 'string & { name: string; }'
I know ways to "force" this partical approach, but I want to understand why this does not work.
let newArray: string[] | { name: string }[] = new Array();
//just a boolean to know when is one type or the other
if (isMultiple) {
otherArray.forEach((item: { name: string }) => {
newArray.push(item)
})
}
else {
otherArray.forEach((item: { name: string }) => {
newArray.push(item.name)
});
}
return newArray
Unless you want to allow mixed arrays (let newArray: (string | { name: string })[]), you can use
// just a boolean to know when is one type or the other
if (isMultiple) {
const newArray: { name: string }[] = [];
otherArray.forEach((item: { name: string }) => {
newArray.push(item)
});
return newArray;
} else {
const newArray: string[] = [];
otherArray.forEach((item: { name: string }) => {
newArray.push(item.name)
});
return newArray;
}
You cant have both types of arrays at the same time. You could do this and define it then create it separately in the if statement
let newArray: string[] | { name: string }[];
//just a boolean to know when is one type or the other
if (isMultiple) {
newArray = new Array< { name : string }>();
otherArray.forEach((item: { name: string }) => {
newArray.push(item)
})
}
else {
newArray = new Array<string>();
otherArrayforEach((item: { name: string }) => {
newArray.push(item.name)
});
}
return newArray