How to get property value in template from associative array in knockout.js ?

Question

JavaScript

Here is such a design:

Item = ko.observableArray();
//...
oneItem().item = item;
oneItem().category = category;

It returns the following contents of oneItem as a result:

oneItem = [
  category: 
    {
    checked: 1,
    name: "Вода",
    title: "Выбрать воду",
    type: "water",
    },
  item:
    {
    color: "Прозрачная",
    id: 2,
    name: "Просто вода",
    price: 100,
    src: "src/water.jpg",
    }
]

In template:

<img class="popup-img" data-bind="attr: { src: oneItem().item.src }"/>
<strong data-bind="text: oneItem().item.color"></strong>

As a result, I get the error Message: Cannot read property 'src' of undefined
But at the same time:
console.log(oneItem().item.src);
shows the required value!
How to access oneItem().item.src in this case?