Type checking with TypeScript

Search…
There are 6 main interfaces that you'll use throughout your experience with Modalfy:
​ModalStackConfig - Interface of the modal stack configuration (needed once).
​ModalOptions - Interface of the modal configuration options.
​ModalProp - Interface of the modal prop exposed by the library.
​ModalComponentProp - Interface of the modal prop exposed by the library (specifically for modal components).
​ModalComponentWithOptions - Interface that adds type support of the modalOptions property (specifically for Hooks modal components).
The 6th and last main interface will actually be provided by you, as Modalfy v2 brought support for modal params type. That interface is going to be used mainly by ModalProp, ModalComponentProp and modalfy(). But for now: let's see how to use the other interfaces we just mentioned.
Please refer to the Types section of the API reference to get a complete overview of each of these interfaces.
ModalStackConfig & ModalOptions
​> ModalStackConfig API​
​> ModalOptions API​
These interfaces should be the ones you use the less. They're the ones that will ensure the type safety of the 2 arguments createModalStack(). So if we were to reuse the same initial example we say in the Creating a stack section, we'd now have:
TypeScript
./App.tsx
import React from 'react'
import {
  ModalOptions,
  ModalStackConfig,
  createModalStack,
  ModalProvider,
} from 'react-native-modalfy'
​
import Navigation from './navigation'
import { ErrorModal } from './components/Modals'
​
const modalConfig: ModalStackConfig = { ErrorModal }
const defaultOptions: ModalOptions = { backdropOpacity: 0.6 }
​
const stack = createModalStack(modalConfig, defaultOptions)
​
const App = () => (
  <ModalProvider stack={stack}>
    <Navigation />
  </ModalProvider>
)
​
​
export default App
And from there, the type checker will get to work and let you know if you're doing something wrong.
If you directly provide the 2 objects instead of using variables like so:
createModalStack({ ErrorModal }, { backdropOpacity: 0.6 })
No need to use these 2 interfaces ascreateModalStack()is already doing it under the hood.
ModalProp
​> ModalProp API​
This interface allows you to type check the modal prop that your regular component will get access to by using withModal() HOC. This means that you'll have to keep a few things in mind:
If you're inside a modal component and not a "regular" component, you should use ModalComponentProp instead.
If you're using useModal() Hook, no need to employModalPropas the Hook itself will take care of all the typing. Simply provide your params interface to the Hook as such useModal<ModalStackParams>()(explained below).
The main and potentially only use case for ModalProp then is when you're using a Class component.
Now that we've covered the gotchas, let's see ModalProp in action. In this example, we created a <PokedexCard/> component that's will open a modal with the full details about a specific Pokemon, with its name, type and entry number in the Pokédex:
Class
Hooks
./components/PokedexCard.tsx
import React from 'react'
import { Text, TouchableOpacity, View } from 'react-native'
import { ModalProp, withModal } from 'react-native-modalfy'
​
import { ModalStackParams } from 'App'
​
interface OwnProps {
  pokemon: ModalStackParams['PokedexEntryModal']['name']
  type: ModalStackParams['PokedexEntryModal']['type']
  id: ModalStackParams['PokedexEntryModal']['id']
}
​
type Props = ModalProp<ModalStackParams, OwnProps>
​
class PokedexCard extends React.Component<Props> {
  onPress = () => {
    const {
      modal: { openModal },
      pokemon,
      type,
      id,
    } = this.props
​
    openModal('PokedexEntryModal', { id, name: pokemon, type })
  }
​
  render() {
    const { id, pokemon, type } = this.props
    return (
      <TouchableOpacity onPress={this.onPress}>
        <View>
          <Text>Nr. {id}Text>
          <Text>{pokemon}</Text>
          <Text>{type}</Text>
          <Text>Show more</Text>
        </View>
      </TouchableOpacity>
    )
  }
}
​
export default withModal(PokedexCard)
// ❌ Don't use ModalProp with the useModal() Hook. If you want to fully type it
// simply proviede your params interface as such: useModal<ModalStackParams>() 
// (ModalStackParams is explained below).
Lots of things are happening in this snippet, but if you're already familiar with TypeScript generics, this should get you excited! Let's dissect this snippet.
#L5 with ModalStackParams. It's an interface you'll have to build that will represent the complete tree of your modals and the types their params are expecting. 
From #L7 to #L11, we're letting TypeScript know that  <PokedexCard/> expects 3 props that should comply with the types specified in ModalStackParams. We're doing this to ensure the type safety of these 3 props because we're using them L#24 to open 'PokedexEntryModal' and pass them as params.
If we were to write ModalStackParams, we can now guesstimate that it could look something like this a minima:
TypeScript
interface ModalStackParams {
  PokedexEntryModal: {
    name: string
    type: string
    id: number
  }
}
You can have a look at the Example provided in the repository and available on Expo to see what ModalStackParamscould look like/be used in a real-world scenario.
You'd also realize that we didn't pass ModalStackParams as a generic to withModal() #L42, instead, we directly provided it to React.Component #L15, via Props created #L13. As you may know, with TypeScript, React.Component is a generic class that accepts up to 2 arguments: React.Component<Props, State>. That's why ModalProp also accepts up to 2 arguments, your params interface and your component props and returns a type with your props type + the new modal prop. There are a few things to notice here:
If you have any State interface, you'll have to provide it to React.Component as a second argument, not ModalProp.
If your component doesn't expect any props, you don't have to provide a second argument to ModalProp. If you want, you can even use it without providing the params type. This means that the most basic way of using ModalProp is class PokedexCard extends React.Component<ModalProp>
On the contrary, providing your params types to ModalProp gives you access to some sweet autocompleting experience (try to see what you get when you trigger it on openModal() for instance)!
ModalComponentProp
​> ModalComponentProp API​
This interface works on the same principles as ModalProp with just some key differences to keep in mind. The first and most important is:
ModalComponentProp should only be used with modal components (rendered by Modalfy)!
 If the component you're working on is not rendered by Modalfy directly/part of your createModalStack() config, you should use ModalProp instead.
Given that we're in a specific modal component, ModalComponentProp accepts a 3rd argument, corresponding to the name of the modal represented by this component. If we reuse our Pokédex example, 'PokedexEntryModal' file could look like:
Hooks
Class
./modals/PokedexEntryModal.tsx
import React from 'react'
import { ModalComponentProp } from 'react-native-modalfy'
​
import { ModalStackParams } from 'App'
​
type Props = ModalComponentProp<
  ModalStackParams,
  void,
  'PokedexEntryModal',
>
​
const PokedexEntryModal = (props: Props) => {
  return (
    // ...
  )
}
​
export default PokedexEntryModal
./modals/PokedexEntryModal.tsx
import React from 'react'
import { ModalComponentProp } from 'react-native-modalfy'
​
import { ModalStackParams } from 'App'
​
type Props = ModalComponentProp<
  ModalStackParams,
  void,
  'PokedexEntryModal',
>
​
class PokedexEntryModal extends React.Component<Props> {
  render() {
    return (
      // ...
    )
  }
}
​
export default PokedexEntryModal
Given that you can reuse the same component for several modals, you can replace that 3rd argument with a union type to make everything work! ie: 
type Props = ModalComponentProp<
  ModalStackParams,
  void,
  'PokedexEntryModal' | 'FavouritePokemonModal',
>
Although you'll never manually render <PokedexEntryModal>yourself, ModalComponentProp voluntarily expects props types as its second argument as your modal component could be getting props from some HOCs. ie:
Class
./modals/PokedexEntryModal.tsx
// ...
​
import { connect } from 'react-redux'
​
// ...
​
import { ReduxState } from 'App'
​
interface OwnProps {
  favouritePokemon: ReduxState['user']['favouritePokemon']
}
​
type Props = ModalComponentProp<
  ModalStackParams,
  OwnProps,
  'PokedexEntryModal',
>
​
class PokedexEntryModal extends React.Component<Props> {
  //...
}
​
const mapStateToProps = (state: ReduxState): OwnProps => {
  favouritePokemon: state.user.favouritePokemon
}
​
export default connect(mapStateToProps)(PokedexEntryModal)
Please check out the ModalComponentProp API reference to have an exhaustive list of what it brings with it.
ModalComponentWithOptions
​> ModalComponentWithOptions API​
ModalComponentWithOptions is only meant to be used with Hooks modal components. If you're working with classes, simply use the staticmodalOptionsproperty as explained below.
As we saw in the Configuring a stack guide, you have 3 different ways to provide options to a modal. While the first 2 are type-checked during the modal stack creation, only the 3rd one involves typing modalOptions from within the modal component itself. 
To do so, simply pass your component props to ModalComponentWithOptions and you're done! The interface will also directly take care of the fact that you're using it on a component, so no need to use React.FC with it. ie:
Hooks
./modals/PokedexEntryModal.tsx
import React from 'react'
import {
  ModalComponentWithOptions,
  ModalComponentProp,
} from 'react-native-modalfy'
​
import { ModalStackParams } from 'App'
​
type Props = ModalComponentProp<
  ModalStackParams,
  void,
  'PokedexEntryModal',
>
​
const PokedexEntryModal: ModalComponentWithOptions<Props> = () => {
  return (
    // ...
  )
}
​
PokedexEntryModal.modalOptions = {
  backdropColor = "rebeccapurple"
}
​
export default PokedexEntryModal
Notice howModalComponentWithOptions<Props> is used right after the modal variable name, not inside the parenthesis of the arrow function!
If you're working with a class, you'll just have to directly type the staticmodalOptions property with the same ModalOptions we used to type our modal stack. eg:
Class
./modals/PokedexEntryModal.tsx
import React from 'react'
import {
  ModalComponentProp,
  ModalOptions
} from 'react-native-modalfy'
​
import { ModalStackParams } from 'App'
​
type Props = ModalComponentProp<
  ModalStackParams,
  void,
  'PokedexEntryModal',
>
​
class PokedexEntryModal extends React.Component<Props> {
  static modalOptions: ModalOptions = {
    backdropColor: 'rebeccapurple'
  }
​
  render() {
    return (
      // ...
    )
  }
}
​
export default PokedexEntryModal