Package ch.njol.skript.lang

Interface Expression<T>

All Superinterfaces:
Debuggable, SyntaxElement
All Known Subinterfaces:
DefaultExpression<T>, Literal<T>
All Known Implementing Classes:
ContainerExpression, ConvertedExpression, ConvertedLiteral, ExpressionList, LiteralList, LiteralString, SimpleExpression, SimpleLiteral, UnparsedLiteral, Variable, VariableString
public interface Expression<T> extends SyntaxElement, Debuggable
Represents an expression. Expressions are used within conditions, effects and other expressions.
See Also:

  • Method Summary

    Modifier and Type
    Method
    Description
    @Nullable Class<?>[]
    acceptChange(Changer.ChangeMode mode)
    Tests whether this expression supports the given mode, and if yes what type it expects the delta to be.
    default @Nullable Object[]
    beforeChange(Expression<?> changed, @Nullable Object[] delta)
    This method is called before this expression is set to another one.
    default boolean
    canBeSingle()
    Whether there's a possibility this could return a single value.
    default boolean
    canReturn(Class<?> returnType)
    Whether this expression might return the following type.
    void
    change(org.bukkit.event.Event event, @Nullable Object[] delta, Changer.ChangeMode mode)
    Changes the expression's value by the given amount.
    default <R> void
    changeInPlace(org.bukkit.event.Event event, Function<T,R> changeFunction)
    Changes the contents of an expression using the given Function.
    default <R> void
    changeInPlace(org.bukkit.event.Event event, Function<T,R> changeFunction, boolean getAll)
    Changes the contents of an expression using the given Function.
    boolean
    check(org.bukkit.event.Event event, Checker<? super T> checker)
    Checks this expression against the given checker.
    boolean
    check(org.bukkit.event.Event event, Checker<? super T> checker, boolean negated)
    Checks this expression against the given checker.
    default Map<Changer.ChangeMode,Class<?>[]>
    getAcceptedChangeModes()
    Tests all accepted change modes, and if so what type it expects the delta to be.
    T[]
    getAll(org.bukkit.event.Event event)
    Gets all possible return values of this expression, i.e.
    boolean
    getAnd()
    Returns true if this expression returns all possible values, false if it only returns some of them.
    T[]
    getArray(org.bukkit.event.Event event)
    Get all the values of this expression.
    <R> @Nullable Expression<? extends R>
    getConvertedExpression(Class<R>... to)
    Tries to convert this expression to the given type.
    default Optional<T>
    getOptionalSingle(org.bukkit.event.Event event)
    Get an optional of the single value of this expression.
    Class<? extends T>
    getReturnType()
    Gets the return type of this expression.
    T
    getSingle(org.bukkit.event.Event event)
    Get the single value of this expression.
    Expression<?>
    getSource()
    Returns the original expression that was parsed, i.e.
    int
    getTime()
     
    boolean
    isDefault()
    Returns whether this value represents the default value of its type for the event, i.e.
    boolean
    isLoopOf(String input)
    Checks whether the given 'loop-...' expression should match this loop, e.g.
    boolean
    isSingle()
     
    @Nullable Iterator<? extends T>
    iterator(org.bukkit.event.Event event)
    Returns the same as getArray(Event) but as an iterator.
    default Class<? extends T>[]
    possibleReturnTypes()
    For expressions that might return multiple (incalculable at parse time) types, this provides a list of all possible types.
    boolean
    setTime(int time)
    Sets the time of this expression, i.e.
    Expression<? extends T>
    simplify()
    Simplifies the expression, e.g.
    default Stream<@NotNull ? extends T>
    stream(org.bukkit.event.Event event)
    Gets a non-null stream of this expression's values.

    Methods inherited from interface ch.njol.skript.lang.Debuggable

    toString, toString

    Methods inherited from interface ch.njol.skript.lang.SyntaxElement

    getParser, init

  • Method Details

    • getSingle

      @Nullable T getSingle(org.bukkit.event.Event event)
      Get the single value of this expression.

      This method may only return null if it always returns null for the given event, i.e. it is equivalent to getting a random element out of getAll(Event) or null iff that array is empty.

      Do not use this in conditions, use check(Event, Checker, boolean) instead.

      Parameters:
      event - The event
      Returns:
      The value or null if this expression doesn't have any value for the event
      Throws:
      UnsupportedOperationException - (optional) if this was called on a non-single expression

    • getOptionalSingle

      default Optional<T> getOptionalSingle(org.bukkit.event.Event event)
      Get an optional of the single value of this expression.

      Do not use this in conditions, use check(Event, Checker, boolean) instead.

      Parameters:
      event - the event
      Returns:
      an Optional containing the single value of this expression for this event.
      See Also:

    • getArray

      T[] getArray(org.bukkit.event.Event event)
      Get all the values of this expression. The returned array is empty if this expression doesn't have any values for the given event.

      The returned array must not contain any null values.

      Do not use this in conditions, use check(Event, Checker, boolean) instead.

      Parameters:
      event - The event
      Returns:
      An array of values of this expression which must neither be null nor contain nulls, and which must not be an internal array.

    • getAll

      T[] getAll(org.bukkit.event.Event event)
      Gets all possible return values of this expression, i.e. it returns the same as getArray(Event) if getAnd() is true, otherwise all possible values for getSingle(Event).
      Parameters:
      event - The event
      Returns:
      An array of all possible values of this expression for the given event which must neither be null nor contain nulls, and which must not be an internal array.

    • stream

      default Stream<@NotNull ? extends T> stream(org.bukkit.event.Event event)
      Gets a non-null stream of this expression's values.
      Parameters:
      event - The event
      Returns:
      A non-null stream of this expression's non-null values

    • isSingle

      boolean isSingle()
      Returns:
      true if this expression will ever only return one value at most, false if it can return multiple values.

    • canBeSingle

      default boolean canBeSingle()
      Whether there's a possibility this could return a single value. Designed for expressions that may return more than one value, but are equally appropriate to use where only singular values are accepted, in which case a single value (out of all available values) will be returned. An example would be functions that return results based on their inputs. Ideally, this will return isSingle() based on its known inputs at initialisation, but for some syntax this may not be known (or a syntax may be intentionally vague in its permissible returns).
      Returns:
      Whether this can be used by single changers
      See Also:

    • check

      boolean check(org.bukkit.event.Event event, Checker<? super T> checker, boolean negated)
      Checks this expression against the given checker. This is the normal version of this method and the one which must be used for simple checks, or as the innermost check of nested checks.

      Usual implementation (may differ, e.g. may return false for nonexistent values independent of negated): 

       return negated ^ check(Event, Checker);
      Parameters:
      event - The event to be used for evaluation
      checker - The checker that determines whether this expression matches
      negated - The checking condition's negated state. This is used to invert the output of the checker if set to true (i.e. negated ^ checker.check(...))
      Returns:
      Whether this expression matches or doesn't match the given checker depending on the condition's negated state.
      See Also:

    • check

      boolean check(org.bukkit.event.Event event, Checker<? super T> checker)
      Checks this expression against the given checker. This method must only be used around other checks, use check(Event, Checker, boolean) for a simple check or the innermost check of a nested check.
      Parameters:
      event - The event to be used for evaluation
      checker - A checker that determines whether this expression matches
      Returns:
      Whether this expression matches the given checker
      See Also:

    • getConvertedExpression

      @Nullable <R> @Nullable Expression<? extends R> getConvertedExpression(Class<R>... to)
      Tries to convert this expression to the given type. This method can print an error prior to returning null to specify the cause.

      Please note that expressions whose returnType is not Object will not be parsed at all for a certain class if there's no converter from the expression's returnType to the desired class. Thus this method should only be overridden if this expression's returnType is Object.

      The returned expression should delegate this method to the original expression's method to prevent excessive converted expression chains (see also ConvertedExpression).

      Parameters:
      to - The desired return type of the returned expression
      Returns:
      Expression with the desired return type or null if the expression can't be converted to the given type. Returns the expression itself if it already returns the desired type.
      See Also:

    • getReturnType

      Class<? extends T> getReturnType()
      Gets the return type of this expression.
      Returns:
      A supertype of any objects returned by getSingle(Event) and the component type of any arrays returned by getArray(Event)

    • possibleReturnTypes

      default Class<? extends T>[] possibleReturnTypes()
      For expressions that might return multiple (incalculable at parse time) types, this provides a list of all possible types. Use cases include: expressions that depend on the return type of their input.
      Returns:
      A list of all possible types this might return

    • canReturn

      default boolean canReturn(Class<?> returnType)
      Whether this expression might return the following type.
      Parameters:
      returnType - The type to test
      Returns:
      true if the argument is within the bounds of the return types

    • getAnd

      boolean getAnd()
      Returns true if this expression returns all possible values, false if it only returns some of them.

      This method significantly influences check(Event, Checker), check(Event, Checker, boolean) and CondIsSet and thus breaks conditions that use this expression if it returns a wrong value.

      This method must return true if this is a single expression. // TODO make this method irrelevant for single expressions

      Returns:
      Whether this expression returns all values at once or only part of them.

    • setTime

      boolean setTime(int time)
      Sets the time of this expression, i.e. whether the returned value represents this expression before or after the event.

      This method will not be called if this expression is guaranteed to be used after a delay (an error will be printed immediately), but will be called if it only can be after a delay (e.g. if the preceding delay is in an if or a loop) as well as if there's no delay involved.

      If this method returns false the expression will be discarded and an error message is printed. Custom error messages must be of ErrorQuality.SEMANTIC_ERROR to be printed (NB: Skript.error(String) always creates semantic errors).

      Parameters:
      time - -1 for past or 1 for future. 0 is never passed to this method as it represents the default state.
      Returns:
      Whether this expression has distinct time states, e.g. a player never changes but a block can. This should be sensitive for the event (using ParserInstance.isCurrentEvent(Class)).
      See Also:

    • getTime

      int getTime()
      Returns:
      The value passed to setTime(int) or 0 if it was never changed.
      See Also:

    • isDefault

      boolean isDefault()
      Returns whether this value represents the default value of its type for the event, i.e. it can be replaced with a call to event.getXyz() if one knows the event invalid input: '&' value type.

      This method might be removed in the future as it's better to check whether value == event.getXyz() for every value an expression returns.

      Returns:
      Whether this is the return types' default expression

    • iterator

      @Nullable @Nullable Iterator<? extends T> iterator(org.bukkit.event.Event event)
      Returns the same as getArray(Event) but as an iterator. This method should be overriden by expressions intended to be looped to increase performance.
      Parameters:
      event - The event to be used for evaluation
      Returns:
      An iterator to iterate over all values of this expression which may be empty and/or null, but must not return null elements.

    • isLoopOf

      boolean isLoopOf(String input)
      Checks whether the given 'loop-...' expression should match this loop, e.g. loop-block matches any loops that loop through blocks and loop-argument matches an argument loop.

      You should usually just return false as e.g. loop-block will automatically match the expression if its returnType is Block or a subtype of it.

      Parameters:
      input - The entered input string (the blank in loop-___)
      Returns:
      Whether this loop matches the given string

    • getSource

      Expression<?> getSource()
      Returns the original expression that was parsed, i.e. without any conversions done.

      This method is undefined for simplified expressions.

      Returns:
      The unconverted source expression of this expression or this expression itself if it was never converted.

    • simplify

      Expression<? extends T> simplify()
      Simplifies the expression, e.g. if it only contains literals the expression may be simplified to a literal, and wrapped expressions are unwrapped.

      After this method was used the toString methods are likely not useful anymore.

      This method is not yet used but will be used to improve efficiency in the future.

      Returns:
      A reference to a simpler version of this expression. Can change this expression directly and return itself if applicable, i.e. no references to the expression before this method call should be kept!

    • acceptChange

      @Nullable @Nullable Class<?>[] acceptChange(Changer.ChangeMode mode)
      Tests whether this expression supports the given mode, and if yes what type it expects the delta to be.

      Use Changer.ChangerUtils.acceptsChange(Expression, ChangeMode, Class...) to test whether an expression supports changing, don't directly use this method!

      Please note that if a changer is registered for this expression's returnType this method does not have to be overridden. If you override it though make sure to return super.acceptChange(mode), and to handle the appropriate ChangeMode(s) in change(Event, Object[], ChangeMode) with super.change(...).

      Unlike Changer.acceptChange(ChangeMode) this method may print errors.

      Parameters:
      mode - The mode to check
      Returns:
      An array of types that change(Event, Object[], ChangeMode) accepts as its delta parameter (which can be arrays to denote that multiple of that type are accepted), or null if the given mode is not supported. For Changer.ChangeMode.DELETE and Changer.ChangeMode.RESET this can return any non-null array to mark them as supported.

    • getAcceptedChangeModes

      default Map<Changer.ChangeMode,Class<?>[]> getAcceptedChangeModes()
      Tests all accepted change modes, and if so what type it expects the delta to be.
      Returns:
      A Map contains ChangeMode as the key and accepted types of that mode as the value

    • change

      void change(org.bukkit.event.Event event, @Nullable @Nullable Object[] delta, Changer.ChangeMode mode)
      Changes the expression's value by the given amount. This will only be called on supported modes and with the desired delta type as returned by acceptChange(ChangeMode)
      Parameters:
      event - The event
      delta - An array with one or more instances of one or more of the classes returned by acceptChange(ChangeMode) for the given change mode (null for Changer.ChangeMode.DELETE and Changer.ChangeMode.RESET). This can be a Object[], thus casting is not allowed.
      mode - The Changer.ChangeMode of the attempted change
      Throws:
      UnsupportedOperationException - (optional) - If this method was called on an unsupported ChangeMode.

    • changeInPlace

      default <R> void changeInPlace(org.bukkit.event.Event event, Function<T,R> changeFunction)
      Changes the contents of an expression using the given Function. Intended for changes that change properties of the values of the expression, rather than completely changing the expression. For example, set vector length of {_v} to 1, rather than set {_v} to vector(0,1,0).
      This is a 1 to 1 transformation and should not add or remove elements. For Variables, this will retain indices. For non-Variables, it will evaluate getArray(Event), apply the change function on each, and call change(Event, Object[], ChangeMode) with the modified values and Changer.ChangeMode.SET.
      Type Parameters:
      R - The output type of the change function. Must be a type returned by {acceptChange(ChangeMode)} for Changer.ChangeMode.SET.
      Parameters:
      event - The event to use for local variables and evaluation
      changeFunction - A 1-to-1 function that transforms a single input to a single output.

    • changeInPlace

      default <R> void changeInPlace(org.bukkit.event.Event event, Function<T,R> changeFunction, boolean getAll)
      Changes the contents of an expression using the given Function. Intended for changes that change properties of the values of the expression, rather than completely changing the expression. For example, set vector length of {_v} to 1, rather than set {_v} to vector(0,1,0).
      This is a 1 to 1 transformation and should not add or remove elements. For Variables, this will retain indices. For non-Variables, it will evaluate the expression, apply the change function on each value, and call change(Event, Object[], ChangeMode) with the modified values and Changer.ChangeMode.SET.
      Type Parameters:
      R - The output type of the change function. Must be a type returned by {acceptChange(ChangeMode)} for Changer.ChangeMode.SET.
      Parameters:
      event - The event to use for local variables and evaluation
      changeFunction - A 1-to-1 function that transforms a single input to a single output.
      getAll - Whether to evaluate with getAll(Event) or getArray(Event).

    • beforeChange

      @Nullable default @Nullable Object[] beforeChange(Expression<?> changed, @Nullable @Nullable Object[] delta)
      This method is called before this expression is set to another one. The return value is what will be used for change. You can use modified version of initial delta array or create a new one altogether

      Default implementation will convert slots to items when they're set to variables, as specified in Skript documentation.

      Parameters:
      changed - What is about to be set.
      delta - Initial delta array.
      Returns:
      Delta array to use for change.