Error map
ActionView::MissingTemplate: Missing template Rails: ActionView::MissingTemplate (Missing template users/show, application/show with {:locale=>[:en], :formats=>[:html], :handlers=>[:erb, :builder, :raw, :ruby, :jbuilder]})
Ruby / Rails · layer 4, Application & API
Centre: this error. First ring: errors it is linked with (8). 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 (8)
Rails: ActionView::Template::Error (undefined method `name' for nil:NilClass): app/views/users/show.html.erb:3
A view called a method on `nil` (or an undefined helper), so rendering failed — the error is wrapped in `ActionView::Template::Er…
Rails: ActionController::RoutingError (No route matches [GET] "/users/new")
The request path/method doesn't match any route in `config/routes.rb` (a 404 in production).
Rails: ActiveRecord::IrreversibleMigration — This migration uses remove_column without a type; db:rollback can't reverse it
`rails db:rollback` can't undo the migration because it contains an operation Rails can't invert.
Rails: ActiveRecord::ConnectionNotEstablished: No connection pool for 'ActiveRecord::Base' found
ActiveRecord has no database connection configured or established for this process.
Rails: ActiveRecord::Deadlocked: PG::TRDeadlockDetected: ERROR: deadlock detected
Two transactions locked rows in opposite orders, so PostgreSQL aborted one.
Rails: ActionController::UnknownFormat — UsersController#show is missing a template for this request format and variant
The controller has no template or `respond_to` handler for the requested format (HTML/JSON/etc.).
Rails: AbstractController::DoubleRenderError (Render and/or redirect were called multiple times in this action. Please note that you may only call render OR redirect, and at most once per action)
An action called `render`/`redirect_to` more than once.
Rails: ActiveRecord::AssociationTypeMismatch: User(#1234) expected, got "42" which is an instance of String(#5678)
You assigned the wrong kind of object (or an id string) to an association.
Two steps away (17)
Ruby: NoMethodError: undefined method `x' for nil (nil:NilClass)
You called a method on nil — the object you expected (a record, hash value, param) wasn’t there.
Rails: ActionController::UrlGenerationError: No route matches {:action=>"show", :controller=>"users", :id=>nil}, missing required keys: [:id]
A URL helper (`user_path(@user)`) was called without a value Rails needs (usually `nil` object).
connect: Network is unreachable (ENETUNREACH)
The host has no route to the destination network — no default gateway, interface down, or trying IPv6 without IPv6 connectivity.
Rails: ActiveRecord::RecordNotFound: Couldn't find User with 'id'=42
`find`/`find_by!` didn't find a row, so Rails raises (and renders a 404 in production).
MySQL ERROR 1146 (42S02): Table 'db.table' doesn't exist
The query references a table that MySQL can’t find in that database.
PostgreSQL: ERROR: relation "x" does not exist
The table/view isn’t found — missing migration, wrong schema, or a case-sensitive quoted name.
MySQL ERROR 1022 (23000): Can't write; duplicate key in table
An ALTER/CREATE produced a duplicate key or constraint name — often a foreign key name that already exists in the database.
Rails: ActionController::InvalidAuthenticityToken (Can't verify CSRF token authenticity)
A non-GET request arrived without a valid CSRF token for the session.
Redis: Error: connect ECONNREFUSED 127.0.0.1:6379 / Could not connect to Redis at 127.0.0.1:6379: Connection refused
Nothing is listening on the Redis host/port your client uses.
Redis: Error: write EPROTO ... SSL routines:ssl3_get_record:wrong version number / Connection reset by peer (TLS vs plaintext)
The client and server disagree about TLS — plaintext client to a TLS port, or TLS client to a plaintext port.
Ruby: NameError: uninitialized constant UsersController::User (Did you mean? Users)
Ruby (or Rails autoloading) couldn't find a class or module with that name in the current scope.
Ruby: NameError: undefined local variable or method 'x' for main:Object
Ruby saw a bare identifier that is neither a local variable nor a method on the current object.
Rails: ActiveRecord::RecordInvalid: Validation failed: Email can't be blank, Name is too short
`save!`/`create!`/`update!` raised because validations failed.
Rails: ActionController::ParameterMissing: param is missing or the value is empty: user
`params.require(:user)` found no `user` key (or it was blank), so Rails responds 400.
Rails: ActiveRecord::PendingMigrationError — Migrations are pending. To resolve this issue, run: bin/rails db:migrate
The database schema is behind the migration files in the app.
Rails: ActiveRecord::StatementInvalid: PG::UndefinedTable: ERROR: relation "users" does not exist
Rails queried a table that isn't in the connected PostgreSQL database.
Rails: ActiveRecord::StatementInvalid: Mysql2::Error: Unknown column 'users.nickname' in 'field list'
The query references a column that doesn't exist in the table (missing migration, typo or stale schema cache).
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