I have defined the `interface` in a `d.ts` file:

```
declare module myModule
{
    interface IQedModel {
        field: string | string[];
        operator: string;

    }
}

```

In an anuglar controller I have implemented it:

```
vm.filters = <myModule.IQedModel>{
    operator: 'and',
    field: []
};

function populateFields() {
    vm.filters.field = [];

    angular.forEach(addedFilters, item => {
        vm.filters.field.push(item.data); //<-- THIS LINE SHOWS ERRORS
    });
}

```

The error is:

> 
> Property 'push' does not exist on type 'string | string[]'
> 
> 
> 

What is the issue here?