渲染函数的 react 参数

Question

我在 flexdashboard 中有一个表格，它的列数可以改变。我可以即时计算列的对齐方式(默认对齐方式将 $23.45 视为字符向量，因此左对齐值，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作为 renderTable 的值传递回 align，因为它是一个 react 值。

如何将 react 性对齐传递回 renderTable 函数的 align 参数？ (或者让我用响应式(Reactive)对齐呈现表格的替代方法)

移动电源

---
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.)

Answer 1

尝试将 aln() 包装在 renderText(...) 中，即

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)