@cala/remote-collection
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A RemoteData Collection class
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Remote-Collection
A TypeScript RemoteData
Collection class
There have been a number of articles written about using Algebraic Data Types to
describe the states that data fetching entails. Replacing isFetching
and other
patterns with explicit expressions of each state is helpful, but there is still
room to improve on the developer experience of dealing with remote data in the
real world. remote-collection
aims to provide a user-friendly experience while
keeping 100% type-safety.
A typical REST API lets you interface with remote Resource
s through well-known
HTTP patterns. A User
resource, for instance, might be accessible by making a
GET https://api.myawesomeapp.com/user/some-id
. You can update parts of that
resource by making a PUT
or PATCH
request to that same URL, or creating a
new resource at that URL by making a POST
request.
A Collection
is typically some ordered list of a Resource
. You might have a
Users
collection, for instance. You can imagine that your API would support
making a request to POST https://api.myawesomeapp.com/user
with a well-formed
User
resource, and it would add that User
resource to the Users
collection. DELETE https://api.myawesomeapp.com/user/some-id
would remove that
User
, etc.
One challenge with dealing with remote resources is identity of a resource
within a collection. Typically, a resource would have an id
field, or some
other unique identifier that you use to tie a given resource to a collection.
But, fetching a collection and then deleting one of the resources is a nested
affair: The request to get the collection (GET /user
), and the request to
delete a resource (DELETE /user/some-id
) both have states, data, failure cases
to account for, etc.
remote-collection
is here to help with that!
Views vs. Resources
The same set of resources might have different ordering, be a filtered set, or
some other smaller subset of the overall set. We call these subsets "views". One
of the requirements of a resource is that it is identifiable by some property.
Typically an id
, uri
, href
, or similar property. The set of those
identified resources are normalized such that updates to that resource should be
visible to other views that might include it.
The state of fetching the whole collection, and the state of each individual
resource are possiblity divergent, so RemoteCollection
stores those states
separately. You may have a failure state in one of your resources, but are
refetching the whole list, and RemoteCollection
tracks both states.
Transitioning the RemoteData state
A helpful cheatsheet for how to transition to the different
RemoteData
states for views vs
individual resources:
| Remote State | View | Resource |
|---|---|---|
|RemoteInitial
|reset
|remove
|
|RemotePending
|refresh
|fetch
|
|RemoteFailure
|withListFailure
|withResourceFailure
|
|RemoteRefresh
|refresh
|fetch
|
|RemoteSuccess
|withList
|withResource
|
Usage
RemoteCollection (Constructor)
Creates a new RemoteCollection
of a generic Resource
type. It takes two
arguments, the first being the key of the identifier on the resource.
Signature
RemoteCollection<Resource extends { [key: string]: any }>(
idProp: keyof Resource
)
Examples
// Initialize a new empty RemoteCollection where the wrapped resource is a `User`
const collection = new RemoteCollection<User>('id');
Resource Methods
fetch
Sets the resource at the given ID to RemotePending
, or if it is already a
RemoteSuccess
or RemoteRefresh
, sets it to RemoteRefresh
. Useful when
making the initial call to the server to indicate that we're currently fetching
this resource, or when updating or re-fetching a resource.
Signature
fetch(id: string): RemoteCollection<Resource>
Examples
const users: User[] = [{ id: 'a', name: 'Alice' }, { id: 'b', name: 'Bob' }];
const collection = new RemoteCollection<User>('id')
.withList(users)
.fetch('a')
.fetch('c');
assert.deepStrictEqual(
collection.find('a'),
RemoteData.refresh({ id: 'a', name: 'Alice' })
);
assert.deepStrictEqual(
collection.find('c'),
RemoteData.pending
);
withResource
Add or update a single Resource. Does not add resource to any views, but does
update the resource based on the idProp
, so if any views are listing that
resource, they will see the update.
If you're trying to add a single resource to a view, you should use
concat
.
Signature
withResource(
resource: Resource
): RemoteCollection<Resource>
Example
const collection = new RemoteCollection<User>('id');
assert.deepStrictEqual(
collection.withResource(users[0]).find(users[0].id),
RemoteData.success(users[0])
);
assert.deepStrictEqual(
collection.withResource(users[0]).view(),
RemoteData.initial
);
assert.deepStrictEqual(
collection.withResource(users[0]).view('team1'),
RemoteData.initial
);
assert.deepStrictEqual(
collection.withList(users).withResource({ id: 'a', name: 'Alison' }).view(),
RemoteData.success([{ id: 'a', name: 'Alison' }, { id: 'b', name: 'Bob' }])
);
withResourceFailure
If requesting a single resource fails, calling this method will store a
RemoteFailure
with the passed string
in the resource map for just this
resource.
Signature
withResourceFailure(id: string, error: string): RemoteCollection<Resource>
find
Lookup a resource by its idProp
. NOTE: If the resource has never been
requested, or has been removed, we return RemoteInitial
indicating that is has
not been retrieved.
Signature
find(id: string): RemoteData<string[], Resource>
Example
const collection = new RemoteCollection<User>('id');
assert.deepStrictEqual(
collection.find('a'),
RemoteData.initial
);
assert.deepStrictEqual(
collection.withResource({ id: 'a', name: 'Alice' }).find('a'),
RemoteData.success({ id: 'a', name: 'Alice' })
);
assert.deepStrictEqual(
collection.withResourceFailure('b', 'Not authorized').find('b'),
RemoteData.failure(['Not authorized'])
);
remove
Removes the resource indicated by the id
.
Signature
remove(id: string): RemoteCollection<Resource>
Examples
const users: User[] = [{ id: 'a', name: 'Alice' }, { id: 'b', name: 'Bob' }];
const collection = new RemoteCollection<User>('id').withList(users);
assert.deepStrictEqual(
collection.view(),
RemoteData.success(users)
);
assert.deepStrictEqual(
collection.remove('a').view(),
RemoteData.success([users[1]])
);
Collection Methods
refresh
Like fetch
but for the whole list. The optional at
arguments allows you to specify
the view key to refresh.
Signature
refresh(viewKey?: string = RemoteCollection.DEFAULT_KEY): RemoteCollection<Resource>
Examples
const users: User[] = [{ id: 'a', name: 'Alice' }, { id: 'b', name: 'Bob' }];
const collection = new RemoteCollection<User>('id');
assert.deepStrictEqual(
collection.refresh().view(),
RemoteData.pending
);
assert.deepStrictEqual(
collection.withList(users).refresh().view(),
RemoteData.refresh(users)
);
assert.deepStrictEqual(
collection.withList(users, 'team1').refresh('team1').view(),
RemoteData.refresh(users)
);
withList
Set or replace the list of resources.
This method adds a list of resources to the RemoteCollection
representing the
normal success-case for fetching the collection at the view key specified by the
second argument, or RemoteCollection.DEFAULT_KEY
if not provided.
Signature
withList(
list: Resource[],
viewKey?: string = RemoteCollection.DEFAULT_KEY
): RemoteCollection<Resource>
Example
const collection = new RemoteCollection<User>('id');
assert.deepStrictEqual(
collection.withList(users).view(),
RemoteData.success(users)
);
assert.deepStrictEqual(
collection.withList(users).view(),
collection.withList(users).view(RemoteCollection.DEFAULT_KEY)
);
assert.deepStrictEqual(
collection.withList(users, 'team1').view('team1'),
RemoteData.success(users)
);
withListFailure
If requesting the list fails, calling this method will store a RemoteFailure
with the passed string
at the view key specified by the second argument, or
RemoteCollection.DEFAULT_KEY
if not provided.
Signature
withListFailure(
error: string,
viewKey?: string = RemoteCollection.DEFAULT_KEY
): Collection<Resource>
view
Return the list of resources at a view key, or default to
RemoteCollection.DEFAULT_KEY
if none is provided.
Signature
public view(viewKey?: string = RemoteCollection.DEFAULT_KEY): RemoteData<string[], Resource[]>
Examples
Here is a break down of what to expect:
If the list was successfully retrieved, and all resources corresponding to the IDs in that list are successful (meaning they haven't later been updated to other
RemoteData
states), you will receive aRemoteSuccess
containing a list of all of the resources.const users: User[] = [{ id: 'a', name: 'Alice' }, { id: 'b', name: 'Bob' }]; const collection = new RemoteCollection<User>('id').withList(users); assert.deepStrictEqual(collection.view(), RemoteData.success(users));
If there was a failure when retrieving the list, you will receive the
RemoteFailure
with the failure string.const collection = new RemoteCollection<User>() .withListFailure('Not authorized'); assert.deepStrictEqual( collection.view(), RemoteData.failure(['Not authorized']) );
If retrieving the list succeeded, but later some subset of the resources had a failure, you will receive all of the failure strings in the
RemoteFailure
.const users: User[] = [ { id: 'a', name: 'Alice' }, { id: 'b', name: 'Bob' }, { id: 'c', name: 'Charlie' } ]; const collection = new RemoteCollection<User>('id') .withList(users) .withResourceFailure('a', 'Bad request') .withResourceFailure('c', 'Conflict'); assert.deepStrictEqual( collection.view(), RemoteData.failure(['Bad request', 'Conflict']) );
If the list, or any resource, is
RemoteInitial
orRemotePending
, you will receive that value, even if some of them areRemoteFailure
,RemoteSuccess
, orRemoteRefresh
.const users: User[] = [ { id: 'a', name: 'Alice' }, { id: 'b', name: 'Bob' }, { id: 'c', name: 'Charlie' } ]; const collection = new RemoteCollection<User>('id') .withList(users) .fetch('d'); assert.deepStrictEqual( collection.view(), RemoteData.pending );
Using a view key:
const collection = new RemoteCollection<User>('id')
.withList(users, 'team1');
assert.deepStrictEqual(
collection.view(),
RemoteData.initial
);
assert.deepStrictEqual(
collection.view('team1'),
RemoteData.success(users);
);
concat
Appends a RemoteCollection
to another. The source
's views are added to the
end of the instance's existing views. The resources in the source
overwrite
any sources with matching idProp
in the instance, and new resources are added.
Signature
concat(
source: RemoteCollection<Resource>
): RemoteCollection<Resource>
Example
Adding resources to the beginning of a view
const users: User[] = [
{ id: 'a', name: 'Alice' },
{ id: 'b', name: 'Bob' }
];
const otherUsers: User[] =[
{ id: 'c', name: 'Charlie' }
];
const existing = new RemoteCollection<User>('id').withList(otherUsers, 'team1');
const collection = new RemoteCollection<User>('id').withList(users, 'team1');
assert.deepStrictEqual(
collection.concat(existing).view('team1'),
RemoteData.success([
{ id: 'a', name: 'Alice' },
{ id: 'b', name: 'Bob' },
{ id: 'c', name: 'Charlie' }
])
);
Adding a single resource to a view
const users = [{ id: 'a', name: 'Alice' }, { id: 'b', name: 'Bob' }];
const newUser = { id: 'd', name: 'Derrick' };
const collection = new RemoteCollection<User>('id').withList(users, 'team1');
const withNewUser = new RemoteCollection<User>().withList([newUser], 'team1')
assert.deepStrictEqual(
collection.concat(withNewUser).view('team1'),
RemoteData.success([
{ id: 'a', name: 'Alice' },
{ id: 'b', name: 'Bob' },
{ id: 'd', name: 'Derrick' }
])
);
union
Unites a RemoteCollection
to another. The source
's views are added to the
end of the instance's existing views. If an item already exists in the
source
's view, it is not appended, such that the item stays in the same place
as it did in the source
's view. The resources in the source
overwrite any
sources with matching idProp
in the instance, and new resources are added.
Signature
union(
source: RemoteCollection<Resource>
): RemoteCollection<Resource>
Example
Adding some items without adding duplicates
const users: User[] = [
{ id: 'a', name: 'Alice' },
{ id: 'b', name: 'Bob' }
];
const otherUsers: User[] =[
{ id: 'a', name: 'Alex' },
{ id: 'c', name: 'Charlie' }
];
const collection = new RemoteCollection<User>('id').withList(users, 'team1');
const updated = new RemoteCollection<User>('id').withList(otherUsers, 'team1');
assert.deepStrictEqual(
collection.union(updated).view('team1'),
RemoteData.success([
{ id: 'a', name: 'Alex' },
{ id: 'b', name: 'Bob' },
{ id: 'c', name: 'Charlie' }
])
);
map
Apply a function to every resource at a view key. Note: Be careful if your
function updates the property at the idProp
, since that could invalidate the
key that is storing the resource.
Signature
map(
fn: (resource: Resource, index: string) => Resource,
viewKey?: string = RemoteCollection.DEFAULT_KEY
): RemoteCollection<Resource>
Example
const users: User[] = [
{ id: 'a', name: 'Alice' },
{ id: 'b', name: 'Bob' }
];
const collection = new RemoteCollection<User>('id').withList(users, 'team1');
assert.deepStrictEqual(
collection.map(u => ({ ...u, name: u.name.toUpperCase() }), 'team1'),
RemoteData.success([
{ id: 'a', name: 'ALICE' },
{ id: 'b', name: 'BOB' }
])
);
omit
Signature
omit(id: string, viewKey?: string = RemoteCollection.DEFAULT_KEY): RemoteCollection<Resource>
Example
const collection = new RemoteCollection<User>('id').withList(users, 'team1');
assert.deepStrictEqual(
collection.view('team1'),
RemoteData.success(users)
);
assert.deepStrictEqual(
collection.omit('a', 'team1').view('team1'),
RemoteData.success([{ id: 'b', name: 'Bob' }])
);
reset
Removes the view at the given view key, or at the
RemoteCollection.DEFAULT_KEY
.
Signature
reset(viewKey?: string = RemoteCollection.DEFAULT_KEY): RemoteCollection<Resource>
Example
const collection = new RemoteCollection<User>('id').withList(users, 'team1');
assert.deepStrictEqual(
collection.view('team1'),
RemoteData.success(users)
);
assert.deepStrictEqual(
collection.reset('team1').view('team1'),
RemoteData.initial
);