React: How to get the child component from the parrent?

How to get the child component from the parrent? This is my attempt:

// This is chunk of code from the 'render' function:
<div className="card-body card-body-rows log-view">
    {, index) => {
                const record = <LogViewRecord
                isSelected={(this as any).selectedRecordId ===} />

            if (!(this as any).selectedRecordId && 0 === index) {
                // I expected the 'record' will be the instance 
                // of my LogViewRecord component (I need to use 
                // it's functions later)...
                (this as any).firstRecord = record;
            return record;

Now I try to use the property, but I get the problem:

componentDidUpdate() : void
    if (!(this as any).selectedRecordId && (this as any).firstRecord) {
        const record = (this as any).firstRecord;

        console.log("record is instance of React.Component:", 
            record instanceof React.Component); // false... Why???
        console.log("record is instance of LogViewRecord:", 
            record instanceof LogViewRecord); // false... Why???

        // I expected 'record' is instance of my LogViewRecord 
        // component and try to use it's switchModel() function, but
        // I get runtime error because it has not.

Why does it happen and how can I fix it?