Is it an anti pattern to have two UI input element for the same value?
Does having two different UI elements for the same input value considered an anti pattern? Both inputs represent the same thing, changing the value of one will update the other.
For example, I wanted to have a slider that the user can select a numeric value from, and a dropdown that displays the value and make it also possible to change it.
No, it is not an anti-pattern as long as it is obvious to the user that both indicators can change the control. In many cases, having more than one way to manipulate a control can be considered a way to improve accessibility. For example, a slider that provides an open text field improves keyboard control.
From https://www.smashingmagazine.com/2017/07/designing-perfect-slider/ :
To provide a shortcut to precise input with a slider, we can use either predefined presets — frequently chosen values or value ranges — or enhance the slider with a text input field fallback. Both presets and the input field could be progressively disclosed — either by a tap on a button or just from a tap on the current value on the slider.
This example allows the user to input text, manipulate with a slider, and manipulate with plus and minus step controls.