# Reactivity API: Utility
## isState()
Determines if a given value is a state object or not.
### Type
```lua
function isState(value: unknown): boolean
```
### Example
```lua
local value = wrap()
print(isState(value)) -- true
value = 0
print(isState(value)) -- false
```
-------------------------------------------------------------------
## unwrap()
Unwraps a state and returns its stored value.
### Type
```lua
function unwrap(value: T | State): T
```
### Details
If given a state, the state's stored value will be returned.
Unwrapping a state within a derived callback will not trigger updates.
Can be given a non-state value, in which case the same value will just be returned.
### Example
```lua
local state = wrap(1)
print(unwrap(state)) -- 1
print(unwrap(1)) -- 1
```
-------------------------------------------------------------------
## readonly()
Creates a new derived state with the same value as the state being derived from.
Used to create readonly states.
### Type
```lua
function readonly(state: State): State
```
### Example
```lua
local count = wrap(1)
local read = readonly(count)
print(read.Value) -- 1
count.Value += 1
print(read.Value) -- 2
read.Value += 1 -- error
```
-------------------------------------------------------------------
## mutate()
Mutates a given state's value and updated any derived states.
### Type
```lua
function mutate(value: T | State): T
```
### Details
Since states only update derived states if a new value is set (tables are compared by reference),
this function serves as a way to trigger derived state updates if a state's value is not changed but
instead mutated.
Can also take non-state as an argument.
### Example
```lua
local state = wrap { Count = 1 }
local derived = derive(function()
return state.Value.Count
end)
mutate(state, function(value)
value.Count += 1
end)
print(derived.Value) -- 2
```
Motivation for this function
```lua
local state = wrap { Count = 1 }
local derived = derive(function()
return state.Value.Count
end)
state.Value.Count += 1
print(derived.Value) -- still 1 because `state.Value` was never set with a new value so change wasn't detected
local value = state.Value
value.Count += 1
state.Value = value
print(derived.Value) -- still 1 because although `state.Value` was set, when the new value set was compared,
-- it was still the same as the previous (tables are compared by reference not their contents)
-- and so no update was made
```