我在 Flexdashboard 中有一个表，其列数可以更改。我可以动态计算列的对齐方式（默认对齐方式$23.45作为字符向量，因此左对齐该值，尽管它是一个数字并且应该右对齐）。问题是我无法将此对齐传递回renderTable作为一个值align因为它是一个无功值。

我怎样才能将反应性对齐传递回renderTable功能align争论？ （或者让我渲染一个具有反应性对齐的表格的替代方案）

MWE

---
title: "test"
output: flexdashboard::flex_dashboard
runtime: shiny
---

```{r}
library(flexdashboard)
library(shiny)
```

Inputs {.sidebar}
-------------------------------------

```{r}
selectInput(
    "ncols", 
    label = "How many columns?",
    choices = 1:5, 
    selected = 5
)
```  

Column  
-------------------------------------

### Test

```{r}
nc <- reactive({input$ncols})
aln <- reactive({substring('lllrr', 1, nc())})

renderTable({
    x <- CO2[1:5, seq_len(nc()), drop = FALSE]
    x[, 1] <- as.character(x[, 1])
    x[3, 1] <- '<b>Mc1</b>'
    x
}, align = aln(), sanitize.text.function = function(x) x)
```

结果是：

 Warning: Error in .getReactiveEnvironment()$currentContext: 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.)

尝试包裹aln() in renderText(...) i.e.

renderTable({
    x <- CO2[1:5, seq_len(nc()), drop = FALSE]
    x[, 1] <- as.character(x[, 1])
    x[3, 1] <- '<b>Mc1</b>'
    x
}, align = renderText(aln()), 
   sanitize.text.function = function(x) x)