interface ModuleA{
width: number;
height: number;
}
interface ModuleB{
width: number;
offset: number;
}
function test(params: ModuleA | ModuleB): any{
console.log(params.offset);
}
TypeScript,
in this case, throws an error to the effect that ModuleA does not have an attribute of offset .
how to solve this problem
in your code params can be ModuleA or ModuleB type. If you pass in a ModuleA type, there is no params.offset attribute, so it fails the check (which is why you use TypeScript), so you report an error, no doubt.
you can take a look at User-Defined Type Guards
.interface ModuleA{
width: number;
height: number;
}
interface ModuleB{
width: number;
offset: number;
}
function isModuleA(param: ModuleA | ModuleB): param is ModuleA {
return (<ModuleA>param).height !== undefined;
}
function test(params: ModuleA | ModuleB): any{
if(isModuleA(params)){
console.log(params.height);
}else{
console.log(params.offset);
}
}
const foo:ModuleA={width:3,height:0};
test(foo); of course, you can also add an optional offset attribute to ModuleA.
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