introduced remotedata selector

src/app/core/data-services/data.service.ts

@@ -6,6 +6,7 @@ import { CacheableObject } from "../cache/object-cache.reducer";
 import { ParamHash } from "../shared/param-hash";
 import { isNotEmpty } from "../../shared/empty.util";
 import { GenericConstructor } from "../shared/generic-constructor";
+import { RemoteData } from "./remote-data";
 
 export abstract class DataService<T extends CacheableObject> {
   abstract serviceName: OpaqueToken;
@@ -16,29 +17,38 @@ export abstract class DataService<T extends CacheableObject> {
 
   }
 
-  findAll(scopeID?: string): Observable<Array<T>> {
+  findAll(scopeID?: string): RemoteData<Array<T>> {
     const key = new ParamHash(this.serviceName, 'findAll', scopeID).toString();
-    return this.requestCache.findAll(key, this.serviceName, scopeID)
-      //get an observable of the IDs from the RequestCache
-      .map(entry => entry.resourceUUIDs)
-      .flatMap((resourceUUIDs: Array<string>) => {
-        // use those IDs to fetch the actual objects from the ObjectCache
-        return this.objectCache.getList<T>(resourceUUIDs, this.modelType);
-      });
+    const requestCacheObs = this.requestCache.findAll(key, this.serviceName, scopeID);
+    return new RemoteData(
+      requestCacheObs.map(entry => entry.isLoading).distinctUntilChanged(),
+      requestCacheObs.map(entry => entry.errorMessage).distinctUntilChanged(),
+      requestCacheObs
+        .map(entry => entry.resourceUUIDs)
+        .flatMap((resourceUUIDs: Array<string>) => {
+          // use those IDs to fetch the actual objects from the ObjectCache
+          return this.objectCache.getList<T>(resourceUUIDs, this.modelType);
+        }).distinctUntilChanged()
+    );
   }
 
-  findById(id: string): Observable<T> {
+  findById(id: string): RemoteData<T> {
     const key = new ParamHash(this.serviceName, 'findById', id).toString();
-    return this.requestCache.findById(key, this.serviceName, id)
-      .map(entry => entry.resourceUUIDs)
-      .flatMap((resourceUUIDs: Array<string>) => {
-        if(isNotEmpty(resourceUUIDs)) {
-          return this.objectCache.get<T>(resourceUUIDs[0], this.modelType);
-        }
-        else {
-          return Observable.of(undefined);
-        }
-      });
+    const requestCacheObs = this.requestCache.findById(key, this.serviceName, id);
+    return new RemoteData(
+      requestCacheObs.map(entry => entry.isLoading).distinctUntilChanged(),
+      requestCacheObs.map(entry => entry.errorMessage).distinctUntilChanged(),
+      requestCacheObs
+        .map(entry => entry.resourceUUIDs)
+        .flatMap((resourceUUIDs: Array<string>) => {
+          if (isNotEmpty(resourceUUIDs)) {
+            return this.objectCache.get<T>(resourceUUIDs[0], this.modelType);
+          }
+          else {
+            return Observable.of(undefined);
+          }
+        }).distinctUntilChanged()
+    );
   }
 
 }

src/app/core/data-services/remote-data.ts

@@ -0,0 +1,75 @@
+import { Observable } from "rxjs";
+import { hasValue } from "../../shared/empty.util";
+
+export enum RemoteDataState {
+  //TODO RequestPending will never happen: implement it in the store & DataEffects.
+  RequestPending,
+  ResponsePending,
+  Failed,
+  Success
+}
+
+/**
+ * A class to represent the state of
+ */
+export class RemoteData<T> {
+
+  constructor(
+    private storeLoading: Observable<boolean>,
+    public errorMessage: Observable<string>,
+    public payload: Observable<T>
+  ) {
+  }
+
+  get state(): Observable<RemoteDataState> {
+    return Observable.combineLatest(
+      this.storeLoading,
+      this.errorMessage.map(msg => hasValue(msg)),
+      (storeLoading, hasMsg) => {
+        if (storeLoading) {
+          return RemoteDataState.ResponsePending
+        }
+        else if (hasMsg) {
+          return RemoteDataState.Failed
+        }
+        else {
+          return RemoteDataState.Success
+        }
+      }
+    ).distinctUntilChanged();
+  }
+
+  get isRequestPending(): Observable<boolean> {
+    return this.state
+      .map(state => state == RemoteDataState.RequestPending)
+      .distinctUntilChanged();
+  }
+
+  get isResponsePending(): Observable<boolean> {
+    return this.state
+      .map(state => state == RemoteDataState.ResponsePending)
+      .distinctUntilChanged();
+  }
+
+  get isLoading(): Observable<boolean> {
+    return this.state
+      .map(state => {
+        return state == RemoteDataState.RequestPending
+          || state === RemoteDataState.ResponsePending
+      })
+      .distinctUntilChanged();
+  }
+
+  get hasFailed(): Observable<boolean> {
+    return this.state
+      .map(state => state == RemoteDataState.Failed)
+      .distinctUntilChanged();
+  }
+
+  get hasSucceeded(): Observable<boolean> {
+    return this.state
+      .map(state => state == RemoteDataState.Success)
+      .distinctUntilChanged();
+  }
+
+}