I am trying to retrieve the first item of type avatar from payload.result within an observable:
let result = this.fileService.getAvatarByUserId(2).pipe(
map((payload: Payload<FileModel[]>) => payload.result),
first((result: FileModel[]) => result.type == 'avatar')
);
However, I keep encountering the error message "is not assignable to type 'Observable'". What is the solution to this issue?
If you have specific requirements, here are a few options to consider...
filter + take(1)
this.fileService.getAvatarByUserId(2)
.pipe(
map((payload: Payload<FileModel[]>) => payload.result),
flatMap(uploads => uploads), // Flattens the array
filter(upload => upload.type === 'avatar'), // filters out non-avatar files
take(1) // retrieves only the first matching file
).subscribe(
console.log
);
OR
first(predicate function) -> my recommendation
this.fileService.getAvatarByUserId(2)
.pipe(
map((payload: Payload<FileModel[]>) => payload.result),
flatMap(uploads => uploads), // Flattens the array
first(upload => upload.type === 'avatar') // returns the first file that meets the condition
).subscribe(
console.log,
console.log // logs an error if no match is found after subscription completion
);
OR filter + first
this.fileService.getAvatarByUserId(2)
.pipe(
map((payload: Payload<FileModel[]>) => payload.result),
flatMap(uploads => uploads), // Flattens the array
filter(upload => upload.type === 'avatar'), // filters out non-avatar files
first() // retrieves the first file in the filtered list
).subscribe(
console.log,
console.log // logs an error if no match is found after subscription completion
);
The first operator can handle errors when the specified condition is not met during subscription completion by using the error method -> check the subscriptions for the last two options (which may explain why I prefer this approach...)
view live demo here
amended to provide clearer explanation of the first operator based on @Jonathan Stellwag's feedback (thank you!!!)
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