Merge pull request #207 from cloudnc/feat/customisable-filter-predicate

feat(Output control): Add option to provide custom predicate for controlling the output filter
cloudnc · Mar 17, 2021 · b04afc5 · b04afc5
2 parents 6dbed3d + 0493115
commit b04afc5
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Showing 2 changed files with 19 additions and 18 deletions.
diff --git a/projects/ngx-sub-form/src/lib/ngx-sub-form.ts b/projects/ngx-sub-form/src/lib/ngx-sub-form.ts
@@ -148,22 +148,19 @@ export function createForm<ControlInterface, FormInterface>(
       if (!isRoot<ControlInterface, FormInterface>(options)) {
         return formGroup.valueChanges.pipe(delay(0));
       } else {
-        if (options.manualSave$) {
-          return options.manualSave$.pipe(
-            withLatestFrom(formGroup.valueChanges),
-            map(([_, formValue]) => formValue),
-            filter(() => formGroup.valid),
-            delay(0),
-            filter(formValue => !isEqual(transformedValue, formValue)),
-          );
-        } else {
-          return formGroup.valueChanges.pipe(
-            filter(() => formGroup.valid),
-            delay(0),
-            filter(formValue => !isEqual(transformedValue, formValue)),
-            options.handleEmissionRate ?? identity,
-          );
-        }
+        const formValues$ = options.manualSave$
+          ? options.manualSave$.pipe(
+              withLatestFrom(formGroup.valueChanges),
+              map(([_, formValue]) => formValue),
+            )
+          : formGroup.valueChanges;
+
+        return formValues$.pipe(
+          filter(() => formGroup.valid),
+          delay(0),
+          filter(formValue => (options.outputFilterPredicate ?? isEqual)(transformedValue, formValue)),
+          options.handleEmissionRate ?? identity,
+        );
       }
     }),
     map(value =>

diff --git a/projects/ngx-sub-form/src/lib/ngx-sub-form.types.ts b/projects/ngx-sub-form/src/lib/ngx-sub-form.types.ts
@@ -89,8 +89,12 @@ export type NgxRootFormOptions<ControlInterface, FormInterface = ControlInterfac
   // if you want to transform it into a manual root form, provide the
   // following observable which trigger a save every time a value is emitted
   manualSave$?: Observable<void>;
-  // @todo it should either be `manualSave$` OR `handleEmissionRate` OR none of them
-  // if you're creating an automatic root form, you can customise the emission rate
+  // The default behavior is to compare the current transformed value of input$ with the current value of the form, and
+  // if these are equal emission on output$ is suppressed to prevent the from broadcasting the current value.
+  // Configure this option to provide your own custom predicate whether or not the form should emit.
+  outputFilterPredicate?: (currentInputValue: FormInterface, outputValue: FormInterface) => boolean;
+  // if you want to control how frequently the form emits on the output$, you can customise the emission rate with this
+  // option. e.g. `handleEmissionRate: formValue$ => formValue$.pipe(debounceTime(300)),`
   handleEmissionRate?: (obs$: Observable<FormInterface>) => Observable<FormInterface>;
 };