Object reference variable is empty at runtime

Why: Your code reads from a '{ref}' reference, but nothing was assigned to it. UE5 doesn't error at compile time, but warns that the runtime access will crash with null-pointer. Fix: Wherever this BP spawns, set the reference via Spawn Actor From Class → Set Reference. If it should be set from outside, expose the variable (eye-icon = Instance Editable) so it's set in the level editor. Add an Is Valid? Branch before each read to gracefully handle null.

Required input pin has no value wired to it

Why: The '{pin}' input on '{node}' must receive a value — either a wire from another node OR a default value in the pin field — but it's empty. Fix: Click on the '{pin}' input field on the '{node}' node. Either type a literal value (e.g. 5 for an integer), or drag a wire from another node's output. If you don't know what to connect, hover over the pin for a tooltip describing what it expects.

PlayAnimMontage call has no actual montage assigned

Why: The Montage pin on PlayAnimMontage is empty (None) or points at a deleted '{m}' asset. Fix: Click the PlayAnimMontage node. In Details, set the Montage to Play pin to a valid AnimMontage asset. If you don't have one yet, create one in Content Browser → right-click → Animation → Animation Montage, target the same skeleton your character uses.

Array Length — get the number of elements in an array

Pure node. Returns 0 for empty arrays.

string

string

Function has a local variable that's never read

Why: You created a local variable '{var}' inside this function, but no node ever reads it after assignment. It's just dead code. Fix: Either: (a) delete the variable and the Set node that writes to it, or (b) add a Get '{var}' node and connect it to wherever you actually need the value (if this was an oversight).

Less (float) — A < B

OR Boolean — logical OR of two booleans

BooleanAND — logical AND

OR=BooleanOR, NOT=Not_PreBool, XOR=BooleanXOR

Integer

A whole number (no decimals). Use for counts, indices, IDs.