# RAN020 Reactive read at template build time

`warning RAN020`: *`count.Value` is read once, when the template is built, so this text never updates.*

**Cause.** `Component.define` builds a template once, when the definition is created, and `setup` and `render`'s props
reader run once per instance, untracked. A reactive read in a static text or attribute, in `renderOf`'s or a
component tag's static props, in setup's returned value, in `render`'s or a component tag's props reader, or in an
element expression's own `if`, `match` or `for` is a snapshot that never updates. A site inside an `arms` function or
an items reader is RAN022's.

**Fix.** Yield or pass a reader (`fun _ -> ...`), or pass the signal and read it where it is used. The rule's fix wraps
a static text, and an attribute whose reader overload returns the value's type.

### Triggers

```fsharp
module Example

open Ranvier
open Ranvier.View
open Ranvier.View.Sugar

let count = createSignal 0

let counter = Component.template (fun _ () -> ()) (span () { string count.Value })
```

### Fixed

```fsharp
module Example

open Ranvier
open Ranvier.View
open Ranvier.View.Sugar

let count = createSignal 0

let counter =
    Component.template (fun _ () -> count) (span () { fun (c: Signal<int>) -> string c.Value })
```

**Suppression.** `// fsharpanalyzer: ignore-line RAN020`, with the reason on the line before. An intended snapshot,
such as an initial value, takes the suppression.