What is the significance of the IRenderFunction interface definition in FluentUI?

Question

What is the significance of the IRenderFunction interface definition in FluentUI?

Recently diving into TypeScript, I've begun working with DetailsList in Fluent UI. Check it out here: https://developer.microsoft.com/en-us/fluentui#/controls/web/detailslist.

I'm exploring the onRenderRow property, which is of type IRenderFunction. More details can be found at: https://github.com/microsoft/fluentui/blob/master/packages/utilities/src/IRenderFunction.ts

In this context, I grasp that props is a generic type P, and defaultRender is a function that takes props as an argument and returns either JSX.Element or null. But why are there parentheses around both? Is it indicative of a function type structure? How should one go about implementing this interface?

(props?: P, defaultRender?: (props?: P) => JSX.Element | null)

Overall, this setup too yields a return type of JSX.Element or null.

typescript typescript-generics fluent-ui fluentui-react

Answer 1

Answer №1

This particular function has two parameters, namely props and defaultRender.

One might wonder about the significance of having parentheses around both of these parameters. Could it represent a specific type of function?

Indeed! The return value of this function is JSX.Element or null.

The first parameter props is denoted as generic type P, while the second one, defaultRender, is categorized as a function that accepts one parameter - props (also a generic type P) and returns JSX.Element | null.

Below is an example illustrating how you can modify the background color of a row:

<DetailsList
  ...
  onRenderRow={(props, defaultRender) => {
    // It's important to consider that props and defaultRender may be undefined
    if (props && defaultRender) {
      return defaultRender({
        ...props,
        styles: {
          ...props.styles,
          root: {
            backgroundColor: '#f00',
          }
        }
      })
    }
    return null;
  }}
/>

Feel free to check out this Codepen for a functional demonstration.

Answer 2

This particular function has two parameters, namely props and defaultRender.

One might wonder about the significance of having parentheses around both of these parameters. Could it represent a specific type of function?

Indeed! The return value of this function is JSX.Element or null.

The first parameter props is denoted as generic type P, while the second one, defaultRender, is categorized as a function that accepts one parameter - props (also a generic type P) and returns JSX.Element | null.

Below is an example illustrating how you can modify the background color of a row:

<DetailsList
  ...
  onRenderRow={(props, defaultRender) => {
    // It's important to consider that props and defaultRender may be undefined
    if (props && defaultRender) {
      return defaultRender({
        ...props,
        styles: {
          ...props.styles,
          root: {
            backgroundColor: '#f00',
          }
        }
      })
    }
    return null;
  }}
/>

Feel free to check out this Codepen for a functional demonstration.

What is the significance of the IRenderFunction interface definition in FluentUI?

Answer №1

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