Do not mutate state directly, Use setState() react/no-direct-mutation-state in React JS

Getting "Do not mutate state directly, Use setState()", Why?

Because, you are mutating the state value inside ref callback method to store the node ref, Here:

this.state.name = input;

---

Solution:

Don't use state variable to store the reference, You can directly store them in component instance because that will not change with time.

As per DOC:

The state contains data specific to this component that may change over time. The state is user-defined, and it should be a plain JavaScript object.

If you don’t use it in render(), it shouldn’t be in the state. For example, you can put timer IDs directly on the instance.

Since you are using controlled input element, ref is not required. Directly use this.state.name with input element value property and this.state.name to access the value.

Use this:

<input
    value={this.state.name || ''}
    name="name"
    type="text"
    className="form-control"
    onChange={this.handleInputChange} 
/>

If you wanted to use ref then store the ref directly on instance, remove value property and you can remove the onChange event also, Use it like this:

<input
    ref={el => this.el = el}
    defaultValue={this.props.str.name}
    name="name"
    type="text"
    className="form-control"
/> 

Now use this ref to access the value like this:

this.el.value