Hook context (ctx)

The object a hook template and a method hook's script receive. The script returns the value to store; undefined or null keeps the game's value.

Field	Meaning
ctx.old	Value before the write
ctx.new	Value the game wrote
ctx.delta	ctx.new - ctx.old
ctx.params	The template's parameters with the hook's values, by name
ctx.state	Object kept between calls, e.g. for counters
ctx.this	Method hooks only: the instance the method runs on; null for static methods
ctx.valueType	The value type, e.g. "int32" or "float"
ctx.address	Address that was written
ctx.writePc	Address of the write instruction
ctx.threadId	Thread that wrote
ctx.hookId	Database id of the hook
ctx.log(…)	Output in the hook log and the debug window

Integer results are truncated and limited to the range of the type. int64 and uint64 values are exact only up to 2^53.

Method hooks

A method hook's script runs before or after the hooked method (When). Besides ctx.params, ctx.state, ctx.this, ctx.log(…) and ctx.hookId it gets:

Field	Meaning
ctx.phase	"before" or "after" the call
ctx.args.<name>	The method's arguments by name. Before the call, assigning one (ctx.args.amount = 0) changes what the method gets.
ctx.result	After the call: the method's result (undefined for void methods). A returned value replaces it.
ctx.refs.<name>	After the call: what ref and out arguments hold
ctx.caller	The innermost hooked call this call runs in, if that hook runs "after the call": an object with .method, .this, .args and .caller; otherwise null
ctx.method	The hooked method
ctx.threadId	Thread the call runs on
ctx.call(method, ...args)	Call a static game method, as in scripts
ctx.static(field)	Mono and IL2CPP: read a static field
ctx.find(className[, objectName]), ctx.forEach(…), ctx.outerName(…)	Find live objects, as in scripts

Objects – ctx.this, object arguments, results – are the same wrappers as in scripts: .name, .className, .field("x"), .get("property"), .call("Method", …), .component("Type"), and fields, properties and methods directly (target.IsPlayer, obj.GetComponentByName("Stats")). Before the call, assigning a field (obj.Field = …) or property (which calls its setter) changes what the method works with.

In Unreal games a hook called from Blueprint bytecode only gets arguments that are simple variables or constants, and only ref arguments can be changed. See Engines for an overview and the HermesQuest examples for method hooks step by step.

The Scripts tab has a ctx of its own, described in the script context reference.