---
title: ResourceState API docs
description: All the API docs of ResourceState
---

# ResourceState API docs

Manages all the different states of a [Resource]:
 - [ResourceUnresolved](#resource-unresolved)
 - [ResourceReady](#resource-ready)
 - [ResourceLoading](#resource-loading)
 - [ResourceError](#resource-error)

## `bool get isLoading`

Returns `true` if the `Resource` is in the loading state.

## `bool get isReady`

Returns `true` if the `Resource` is in the ready state.

## `bool get hasError`

Returns `true` if the `Resource` is in the error state.

## `bool get isRefreshing`

Returns `true` if the `Resource` is being refreshed.

## `ResourceReady<T>? get asReady`

Upcast __ResourceState__ into a __ResourceReady__, or return null if the __ResourceState__ is in loading/error state.

## `ResourceReady<T>? get asError`

Upcast __ResourceState__ into a __ResourceError__, or return null if the __ResourceState__ is in read/loading state.

## `T? get value`

Attempts to synchronously get the value of __ResourceReady__.

On error, this will rethrow the error.
If loading, will return `null`.

## `T? call()`

Attempts to synchronously get the value of __ResourceReady__.

On error, this will rethrow the error.
If loading, will return `null`.

## `Object get error`

Attempts to synchronously get the error of __ResourceError__.

On other states will return `null`.

## `R maybeMap<R>({required R Function() orElse, R Function(ResourceReady<T> ready)? ready, R Function(ResourceError<T> error)? error, R Function(ResourceLoading<T> loading)? loading})`

Perform some actions based on the state of the __ResourceState__, or call orElse if the current state is not considered.

```dart
resourceState.maybeMap(
  ready: (resourceReady) => Text(resourceReady.value),
  orElse: () => const SizedBox(),
);
```

The function above renders the `Text` widget only in the `ready` state, for all other state the `orElse` function is called.

Prefer using the `maybeOn` method if you are not interested in the `ResourceState` object.

## `R on<R>({required R Function(T data) ready, required R Function(Object error, StackTrace? stackTrace) error, required R Function() loading})`

Performs an action based on the state of the __ResourceState__.

All cases are required.

```dart
resourceState.when(
  ready: (data) => Text('ready: $data'),
  error: (error, stackTrace) => Text('error: $error $stackTrace'),
  loading: () => Text('loading'),
);
```

## `R maybeOn<R>({required R Function() orElse, R Function(T data)? ready, R Function(Object error, StackTrace? stackTrace)? error, R Function()? loading})`

Performs an action based on the state of the __ResourceState__, or call __orElse__ if the current state is not considered.

```dart
resourceState.maybeOn(
  ready: (data) => Text(data),
  orElse: () => const SizedBox(),
);
```

The function above renders the `Text` widget only in the `ready` state, for all other state the `orElse` function is called.

## Resource Unresolved

The `ResourceUnresolved` state indicates that the `Resource` is not resolved yet, this state is internal and should never be visible outside.

## Resource Ready

The `ResourceReady` state indicates that the `Resource` is resolved and ready to use.

### Constructor

```dart
ResourceReady(T value, {bool isRefreshing = false});
```

`value` is the resolved value of the `Resource`.
`isRefreshing` is `true` if the `Resource` is being refreshed.

### `String toString()`

Returns the string representation of the `ResourceReady` state.

### `ResourceReady<T> copyWith({T? value, bool? isRefreshing})`

Convenience method to copy the current state and create a new `ResourceReady` state with the overridden values.

## Resource Loading

The `ResourceLoading` state indicates that the `Resource` is loading.

### `String toString()`

Returns the string representation of the `ResourceLoading` state.

## Resource Error

The `ResourceError` state indicates that the `Resource` failed to load and is in an error state.

### Constructor

```dart
ResourceError(
  Object error, {
  StackTrace? stackTrace,
  bool isRefreshing = false,
});
```

`error` is the error that occurred.
`stackTrace` is the stack trace of the error, if present.
`isRefreshing` is `true` if the `Resource` is being refreshed.

### `String toString()`

Returns the string representation of the `ResourceError` state.

### `ResourceError<T> copyWith({Object? error, StackTrace? stackTrace, bool? isRefreshing})`

Convenience method to copy the current state and create a new `ResourceError` state with the overridden values.

## Sealed class

__ResourceState__ is a sealed class, so you can perform a switch on the different states instead of using `on`, `maybeOn`, etc.

```dart
return switch (userState) {
  ResourceReady(:final value) => Text(value),
  ResourceError(:final error, :final stackTrace) =>
    Text('$error, $stackTrace'),
  ResourceLoading() => const CircularProgressIndicator(),
}
```