Dynamic branches and lists

This reference documents every current public declaration in this part of Pine. Examples run inside App.Mount(), a component factory, or an explicit UI.Root(...) unless they only create state/configuration. Explicit UI.Mount(...) remains available for advanced ownership. Variable names such as count, items and label refer to the typed values described by each example. All APIs run on Unity’s main thread.

`Branch`

Branch<T>

A constructed dynamic result and its optional exit retention delay in seconds. Presence becomes false immediately on removal while the result remains alive for ExitDelay; reentry before expiration cancels removal and reuses its scope. Zero delay removes immediately. Delays must be finite and non-negative.

Type parameter	Meaning
`T`	Typed value, native result or identity contract; see the summary for its role.

UI.Show(
    condition: () => true,
    build: present => new Branch<UnityEngine.Component>(
        UI.Label(text: () => present.Value ? "Present" : "Leaving"),
        0.2
    )
);

`Branch.Value`

T Value

The native or custom result retained by this branch's scope.

UnityEngine.Component result = branch.Value;

`Branch.ExitDelay`

double ExitDelay

Finite non-negative seconds to retain an exiting branch after its presence becomes false. Zero removes immediately.

double seconds = branch.ExitDelay;

`Branch.Branch`

public Branch(T value, double exitDelay = 0)

Constructs this value with the supplied typed arguments. A constructed dynamic result and its optional exit retention delay in seconds. Presence becomes false immediately on removal while the result remains alive for ExitDelay; reentry before expiration cancels removal and reuses its scope. Zero delay removes immediately. Delays must be finite and non-negative.

Parameter	Meaning
`value`	The typed value or reactive input to read/apply; sources remain observable for the owning lifetime.
`exitDelay`	Finite non-negative seconds to retain a branch after presence becomes false.

UI.Show(
    condition: () => true,
    build: present => new Branch<UnityEngine.Component>(
        UI.Label(text: () => present.Value ? "Present" : "Leaving"),
        0.2
    )
);

`Branch.implicit`

public static implicit operator Branch<T>(T value)

Converts a constructed result into a branch with zero exit delay. Use the explicit constructor for retained exit animation.

Parameter	Meaning
`value`	The typed value or reactive input to read/apply; sources remain observable for the owning lifetime.

Returns: A typed Value adapter that reads this reactive value when evaluated; the conversion does not write to its source.

Branch<string> branch = "Ready";

`UI.Show`

public static ReadOnly<IReadOnlyList<TResult>> Show<TResult>(Func<bool> condition, Func<TResult> build, Func<TResult> fallback = null)

Constructs an owned conditional branch while its condition is true, with an optional fallback. The predicate overload retains the last truthy value for its branch. Results and presence are read-only; exit delays retain native results while presence is false, and reentry reuses unexpired scopes.

Type parameter	Meaning
`TResult`	Typed value, native result or identity contract; see the summary for its role.

Parameter	Meaning
`condition`	Reactive visibility predicate; its reads establish the controlling dependencies.
`build`	Construction callback executed in its documented ownership scope; declare owned resources here.
`fallback`	Optional construction callback used when the selected primary branch is absent.

Returns: An observable, immutable list of current and retained-exit branch results.

Ownership: Construct and apply declarations on Unity's main thread within UI.Mount, UI.Root or a live Scope.Run. Literal assignments occur once; reactive observers and handlers end with their owning scope.

var result = UI.Show(
    condition: () => visible.Value,
    build: () => UI.Label(text: "Visible")
);
UI.Frame(UI.Children(read: () => result.Value));

`UI.Switch`

public static ReadOnly<IReadOnlyList<TResult>> Switch<TKey, TResult>(Func<TKey> select, Func<TKey, TResult> build, IEqualityComparer<TKey> comparer = null)

Retains the selected keyed branch and optionally its exiting predecessor. Selection keys must be non-null; a comparer controls identity. Dictionary overloads support a fallback. Branch callbacks run only when creating that keyed scope, and returned presence/output are read-only.

Type parameter	Meaning
`TKey`	Typed value, native result or identity contract; see the summary for its role.
`TResult`	Typed value, native result or identity contract; see the summary for its role.

Parameter	Meaning
`select`	Native event selector or reactive branch selector, as specified by this overload.
`build`	Construction callback executed in its documented ownership scope; declare owned resources here.
`comparer`	Optional equality/identity comparer; null selects the documented default policy.

Returns: An observable, immutable list of selected and retained-exit branch results.

var result = UI.Switch(
    select: () => page.Value,
    build: key => UI.Label(text: key)
);
UI.Frame(UI.Children(read: () => result.Value));

`UI.Indexes`

public static ReadOnly<IReadOnlyList<TResult>> Indexes<TValue, TResult>(Func<IReadOnlyList<TValue>> read, Func<int, ReadOnly<TValue>, TResult> build)

Retains rows by index or explicit dictionary key, updating each row's read-only reactive value. Use explicit stable item IDs to preserve rows across reordering or immutable item replacement. Keys must be unique and non-null. Presence supports delayed exits through Branch.

Type parameter	Meaning
`TValue`	Typed value, native result or identity contract; see the summary for its role.
`TResult`	Typed value, native result or identity contract; see the summary for its role.

Parameter	Meaning
`read`	The getter whose source reads establish reactive dependencies; supply a stable native result where required.
`build`	Construction callback executed in its documented ownership scope; declare owned resources here.

Returns: An observable, immutable ordered list of row results; retained rows keep native identity.

var rows = UI.Indexes(
    read: () => items.Value,
    build: (index, item) => UI.Label(text: () => item.Value)
);
UI.Column(UI.Children(read: () => rows.Value));

`UI.Values`

public static ReadOnly<IReadOnlyList<TResult>> Values<TValue, TResult>(Func<IReadOnlyList<TValue>> read, Func<TValue, ReadOnly<int>, TResult> build, IEqualityComparer<TValue> comparer = null)

Retains rows by value identity and exposes each current index as a read-only reactive value. Reordering preserves constructed rows; removed rows report index -1 and false presence during delayed exit. Duplicate or null identity values are rejected, and an optional comparer controls identity.

Type parameter	Meaning
`TValue`	Typed value, native result or identity contract; see the summary for its role.
`TResult`	Typed value, native result or identity contract; see the summary for its role.

Parameter	Meaning
`read`	The getter whose source reads establish reactive dependencies; supply a stable native result where required.
`build`	Construction callback executed in its documented ownership scope; declare owned resources here.
`comparer`	Optional equality/identity comparer; null selects the documented default policy.

Returns: An observable, immutable ordered list of row results; indices are read-only operator-owned state.

var rows = UI.Values(
    read: () => items.Value,
    build: (item, index) => UI.Label(text: () => $"{index.Value}: {item}")
);
UI.Column(UI.Children(read: () => rows.Value));

`UI.Switch`

public static ReadOnly<IReadOnlyList<TResult>> Switch<TKey, TResult>(Func<TKey> select, Func<TKey, ReadOnly<bool>, Branch<TResult>> build, IEqualityComparer<TKey> comparer = null)

Type parameter	Meaning
`TKey`	Typed value, native result or identity contract; see the summary for its role.
`TResult`	Typed value, native result or identity contract; see the summary for its role.

Parameter	Meaning
`select`	Native event selector or reactive branch selector, as specified by this overload.
`build`	Construction callback executed in its documented ownership scope; declare owned resources here.
`comparer`	Optional equality/identity comparer; null selects the documented default policy.

Returns: An observable, immutable list of selected and retained-exit branch results.

var result = UI.Switch(
    select: () => page.Value,
    build: key => UI.Label(text: key)
);
UI.Frame(UI.Children(read: () => result.Value));

public static ReadOnly<IReadOnlyList<TResult>> Switch<TKey, TResult>(Func<TKey> select, IReadOnlyDictionary<TKey, Func<ReadOnly<bool>, Branch<TResult>>> branches, Func<ReadOnly<bool>, Branch<TResult>> fallback = null)

Type parameter	Meaning
`TKey`	Typed value, native result or identity contract; see the summary for its role.
`TResult`	Typed value, native result or identity contract; see the summary for its role.

Parameter	Meaning
`select`	Native event selector or reactive branch selector, as specified by this overload.
`branches`	Construction callbacks indexed by non-null identity keys.
`fallback`	Optional construction callback used when the selected primary branch is absent.

Returns: An observable, immutable list of selected and retained-exit branch results.

var result = UI.Switch(
    select: () => page.Value,
    build: key => UI.Label(text: key)
);
UI.Frame(UI.Children(read: () => result.Value));

`UI.Show`

public static ReadOnly<IReadOnlyList<TResult>> Show<TResult>(Func<bool> condition, Func<ReadOnly<bool>, Branch<TResult>> build, Func<ReadOnly<bool>, Branch<TResult>> fallback = null)

Type parameter	Meaning
`TResult`	Typed value, native result or identity contract; see the summary for its role.

Parameter	Meaning
`condition`	Reactive visibility predicate; its reads establish the controlling dependencies.
`build`	Construction callback executed in its documented ownership scope; declare owned resources here.
`fallback`	Optional construction callback used when the selected primary branch is absent.

Returns: An observable, immutable list of current and retained-exit branch results.

var result = UI.Show(
    condition: () => visible.Value,
    build: () => UI.Label(text: "Visible")
);
UI.Frame(UI.Children(read: () => result.Value));

public static ReadOnly<IReadOnlyList<TResult>> Show<T, TResult>(Func<T> read, Predicate<T> truthy, Func<ReadOnly<T>, ReadOnly<bool>, Branch<TResult>> build, Func<ReadOnly<bool>, Branch<TResult>> fallback = null)

Type parameter	Meaning
`T`	Typed value, native result or identity contract; see the summary for its role.
`TResult`	Typed value, native result or identity contract; see the summary for its role.

Parameter	Meaning
`read`	The getter whose source reads establish reactive dependencies; supply a stable native result where required.
`truthy`	Predicate determining whether the read value belongs to the visible branch.
`build`	Construction callback executed in its documented ownership scope; declare owned resources here.
`fallback`	Optional construction callback used when the selected primary branch is absent.

Returns: An observable, immutable list of current and retained-exit branch results.

var result = UI.Show(
    condition: () => visible.Value,
    build: () => UI.Label(text: "Visible")
);
UI.Frame(UI.Children(read: () => result.Value));

`UI.Indexes`

public static ReadOnly<IReadOnlyList<TResult>> Indexes<TKey, TValue, TResult>(Func<IEnumerable<KeyValuePair<TKey, TValue>>> read, Func<TKey, ReadOnly<TValue>, ReadOnly<bool>, Branch<TResult>> build, IEqualityComparer<TKey> comparer = null)

Type parameter	Meaning
`TKey`	Typed value, native result or identity contract; see the summary for its role.
`TValue`	Typed value, native result or identity contract; see the summary for its role.
`TResult`	Typed value, native result or identity contract; see the summary for its role.

Parameter	Meaning
`read`	The getter whose source reads establish reactive dependencies; supply a stable native result where required.
`build`	Construction callback executed in its documented ownership scope; declare owned resources here.
`comparer`	Optional equality/identity comparer; null selects the documented default policy.

Returns: An observable, immutable ordered list of row results; retained rows keep native identity.

var rows = UI.Indexes(
    read: () => items.Value,
    build: (index, item) => UI.Label(text: () => item.Value)
);
UI.Column(UI.Children(read: () => rows.Value));

public static ReadOnly<IReadOnlyList<TResult>> Indexes<TValue, TResult>(Func<IReadOnlyList<TValue>> read, Func<int, ReadOnly<TValue>, ReadOnly<bool>, Branch<TResult>> build)

Type parameter	Meaning
`TValue`	Typed value, native result or identity contract; see the summary for its role.
`TResult`	Typed value, native result or identity contract; see the summary for its role.

Parameter	Meaning
`read`	The getter whose source reads establish reactive dependencies; supply a stable native result where required.
`build`	Construction callback executed in its documented ownership scope; declare owned resources here.

Returns: An observable, immutable ordered list of row results; retained rows keep native identity.

var rows = UI.Indexes(
    read: () => items.Value,
    build: (index, item) => UI.Label(text: () => item.Value)
);
UI.Column(UI.Children(read: () => rows.Value));

`UI.Values`

public static ReadOnly<IReadOnlyList<TResult>> Values<TValue, TResult>(Func<IReadOnlyList<TValue>> read, Func<TValue, ReadOnly<int>, ReadOnly<bool>, Branch<TResult>> build, IEqualityComparer<TValue> comparer = null)

Type parameter	Meaning
`TValue`	Typed value, native result or identity contract; see the summary for its role.
`TResult`	Typed value, native result or identity contract; see the summary for its role.

Parameter	Meaning
`read`	The getter whose source reads establish reactive dependencies; supply a stable native result where required.
`build`	Construction callback executed in its documented ownership scope; declare owned resources here.
`comparer`	Optional equality/identity comparer; null selects the documented default policy.

Returns: An observable, immutable ordered list of row results; indices are read-only operator-owned state.

var rows = UI.Values(
    read: () => items.Value,
    build: (item, index) => UI.Label(text: () => $"{index.Value}: {item}")
);
UI.Column(UI.Children(read: () => rows.Value));

Branch​

Branch.Value​

Branch.ExitDelay​

Branch.Branch​

Branch.implicit​

UI.Show​

UI.Switch​

UI.Indexes​

UI.Values​

UI.Switch​

UI.Show​

UI.Indexes​

UI.Values​

`Branch`

`Branch.Value`

`Branch.ExitDelay`

`Branch.Branch`

`Branch.implicit`

`UI.Show`

`UI.Switch`

`UI.Indexes`

`UI.Values`

`UI.Switch`

`UI.Show`

`UI.Indexes`

`UI.Values`