Error map
Main Thread Checker Main Thread Checker: UI API called on a background thread: -[UIView setNeedsLayout]
iOS · layer 1, On your device
Centre: this error. First ring: errors it is linked with (12). Outer ring: what those are linked with. Colours show the layer of a request each error belongs to. Click any dot to re-centre the map on it; hover to follow its connections. The centre dot opens the error page.
Directly related (12)
Operation cannot be fulfilled on deployments.apps "x": the object has been modified; please apply your changes to the latest version and try again
Optimistic-concurrency conflict: the object changed (new resourceVersion) between when you read it and when you tried to update i…
Go: fatal error: all goroutines are asleep - deadlock!
Every goroutine is blocked waiting (on a channel, mutex or WaitGroup), so the program can never continue.
CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views
Background code updated a View directly; UI changes must happen on the main thread.
ERROR: could not serialize access due to concurrent update
A REPEATABLE READ/SERIALIZABLE transaction conflicted with a concurrent one and must be retried.
API Error: Too many concurrent requests (concurrency limit reached)
You have more requests in flight at once than the API allows for your key — even if your requests-per-minute rate is fine.
java.lang.InterruptedException (sleep interrupted)
A blocked thread (sleep, wait, join, queue take) was interrupted by another thread.
ConditionalCheckFailedException: The conditional request failed
A write’s ConditionExpression evaluated to false, so DynamoDB didn’t perform it — often exactly as designed.
NSUnknownKeyException: this class is not key value coding-compliant for the key x
A storyboard/XIB has a connection to an outlet or action that no longer exists in the class (renamed or deleted), or the view’s c…
unable to dequeue a cell with identifier Cell - must register a nib or a class for the identifier or connect a prototype cell in a storyboard
The table/collection view was asked for a reusable cell identifier that was never registered.
SwiftUI: Publishing changes from background threads is not allowed; make sure to publish values from the main thread
An ObservableObject’s @Published property was updated from a background thread.
Auto Layout: Unable to simultaneously satisfy constraints. Probably at least one of the constraints in the following list is one you don't want
Two or more Auto Layout constraints conflict; UIKit breaks one to recover and logs this message.
Swift 6: Main actor-isolated property 'x' can not be referenced from a nonisolated context / Sending 'x' risks causing data races
Strict concurrency checking found code that accesses main-actor state from another isolation domain, or passes non-Sendable value…
Two steps away (33)
HTTP 409 Conflict
The request conflicts with the current state of the resource — e.g. a duplicate or an edit based on an outdated version.
java.util.ConcurrentModificationException
A collection was modified while being iterated (even in a single thread).
HTTP 412 Precondition Failed
A conditional request header (If-Match, If-Unmodified-Since) didn’t match the current state of the resource.
HTTP 428 Precondition Required
The server requires a conditional request (If-Match / If-Unmodified-Since) to prevent lost updates, and you didn’t send one.
java.util.concurrent.TimeoutException
A Future.get(timeout) or async operation didn’t complete in the allowed time.
Optimistic lock conflict: OptimisticLockException / StaleObjectStateException / version mismatch
Someone else changed the record after you read it, so your update — based on an old version — was rejected to avoid overwriting t…
AAPT: error: resource android:attr/lStar not found
A dependency (androidx.core 1.7+) uses an attribute from Android 12 (API 31), but your module compiles against an older compileSd…
AAPT: error: resource x (aka y) not found — Android resource linking failed
A layout, manifest or style references a resource (drawable, string, style, attribute) that doesn’t exist in the module or its de…
android.os.NetworkOnMainThreadException
The app made a network call on the main (UI) thread, which Android forbids.
Deadlock found when trying to get lock; try restarting transaction
Two transactions waited on each other’s locks; the database killed one so the other could continue.
MySQL ERROR 1213 (40001): Deadlock found when trying to get lock; try restarting transaction
MySQL detected a deadlock between two transactions and rolled one back.
FATAL: terminating connection due to idle-in-transaction timeout
A session opened a transaction and sat idle longer than idle_in_transaction_session_timeout.
AWS: ThrottlingException / Rate exceeded
You exceeded the request rate for an AWS API; retry with exponential backoff.
HTTP 429 Too Many Requests
You’ve hit a rate limit — too many requests in a given time window. Slow down and retry later.
API Request Timed Out (ETIMEDOUT / ReadTimeout / timeout of 30000ms exceeded)
The client gave up waiting — either for the connection to open or for the response to arrive.
API Error: Idempotency key reused with different parameters (idempotency_key_in_use)
An Idempotency-Key header was sent again with a different request body, or while the first request with that key was still runnin…
Conflict: AnotherOperationInProgress — Another operation is in progress on the resource
Azure is still processing a previous change on the same resource, so new operations are rejected until it finishes.
EF Core: A second operation was started on this context instance before a previous operation completed
The same DbContext was used concurrently — async calls not awaited, parallel tasks sharing a context, or a context registered as…
API Error: Resource already exists (ALREADY_EXISTS / resource_already_exists / 409)
The create request was refused because an object with the same unique identity — name, email, external ID — already exists.
ProvisionedThroughputExceededException: The level of configured provisioned throughput for the table was exceeded
Requests exceed the table’s (or index’s) provisioned read/write capacity, or one partition is hot.
DynamoDB ValidationException: One or more parameter values were invalid: Missing the key pk in the item / The provided key element does not match the schema
The item or key doesn’t match the table’s primary key schema — wrong attribute name, wrong type, or missing sort key.
App Transport Security has blocked a cleartext HTTP resource load
iOS blocked an `http://` request (or a weak-TLS HTTPS one) because App Transport Security requires secure connections.
Thread 1: signal SIGABRT (app crashes with "libc++abi: terminating")
The app deliberately aborted — an uncaught exception, failed assertion or fatalError. The console above the crash has the real me…
Building for iOS Simulator, but linking in object file built for iOS, for architecture arm64
A library contains device-only arm64 code; Apple Silicon simulators also run arm64 and need a separate simulator slice.
Swift: Could not cast value of type 'X' to 'Y'
A force cast (as!) failed because the object isn’t the expected type.
Unable to Install "App": This app cannot be installed because its integrity could not be verified
iOS rejected the app because its signature doesn’t validate for this device — expired/revoked certificate, ad-hoc profile without…
SwiftUI: Modifying state during view update, this will cause undefined behavior
A @State/@Published value was changed while SwiftUI was computing a view’s body.
Swift: Escaping closure captures mutating 'self' parameter
A mutating method of a struct tries to capture self in an escaping closure, which Swift forbids.
SwiftUI Preview: Cannot preview in this file — the preview crashed / failed to build
Xcode Previews couldn’t build or run the view — compile errors elsewhere, a crash in preview data, or preview-specific environmen…
Swift: Cannot convert value of type 'X' to expected argument type 'Y'
The value’s type doesn’t match what the function or property expects.
Swift: Fatal error: Index out of range
Code accessed an array index that doesn’t exist — empty arrays, off-by-one loops, or data changing while a table reloads.
Swift: 'X' is only available in iOS 16.0 or newer
You used an API that requires a newer iOS than your deployment target.
Swift: Reference to property 'x' in closure requires explicit use of 'self' to make capture semantics explicit
In an escaping closure inside a class, Swift requires self. to make the capture (and potential retain cycle) visible.
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