setState error for onclick in react

Question

I'm get this error Warning: setState(...): Cannot update during an existing state transition (such as within render or another component's constructor). Render methods should be a pure function of props and state; constructor side-effects are an anti-pattern, but can be moved to componentWillMount for

<a key={brand} onClick={this.someFn(Brands[brand])}>

Answer 1

 <a key={brand} onClick={() => this.someFn(Brands[brand])}>

用箭头功能调用它

Answer 2

I strongly advise against mutating the state inside render() methods. In fact it is strongly suggested by the maintainers of React, to keep the render() method as a pure function.

If you want to change the state between different components, for example if you have a sidebar, the most robust solution is to use Redux or an equivalent application state library.