Reavtivity question

shiny
, ,
1

Hi guys,

I have a question related to reactive values to better understand those. I was trying to create a reactive value with reactiveVal for which the content should be the subset of a different reactive value and the filtering based on a user input. Basically something like that:

reactiveValue_2 <- reactiveVal(reactiveValue_1()[ID == input$selectedId])

However, this gives me the error Operation not allowed without an active reactive context. (You tried to do something that can only be done from inside a reactive expression or observer.). When I put everything into something like that, it works:

reactiveValue_2 <- reactiveVal()
observeEvent(input$selectedId, {
    reactiveValue_2(reactiveValue_1()[ID == input$selectedId])
})

Could somebody explain to me why the first reason does not work? I would love to understand the mechanics behind that.

Best regards
Jakob

2

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