Class SafeComparer

Null-safe delegating comparator.

Inheritance

object

SafeComparer

EntryComparer

InverseComparer

Implements

Inherited Members

object.Equals(object, object)

object.GetType()

object.MemberwiseClone()

object.ReferenceEquals(object, object)

Namespace: Tangosol.Util.Comparator

Assembly: Coherence.dll

Syntax

public class SafeComparer : IQueryCacheComparer, IEntryAwareComparer, IComparer, IPortableObject

Remarks

null values are evaluated as "less then" any non-null value. If the wrapped comparator is not specified then all non-null values must implement the IComparable interface.

Use SafeComparer.Instance to obtain an instance of non-delegating SafeComparer.

Constructors

SafeComparer()

Default constructor.

Declaration

public SafeComparer()

SafeComparer(IComparer)

Construct a SafeComparer delegating to the specified (wrapped) comparer.

Declaration

public SafeComparer(IComparer comparer)

Parameters

Type	Name	Description
IComparer	comparer	IComparer object to delegate comparison of non-null values (optional).

Fields

Instance

The trivial SafeComparer.

Declaration

public static readonly SafeComparer Instance

Field Value

Type	Description
SafeComparer

m_comparer

The wrapped IComparer.

Declaration

protected IComparer m_comparer

Field Value

Type	Description
IComparer

Properties

Comparer

The wrapped IComparer.

Declaration

public virtual IComparer Comparer { get; }

Property Value

Type	Description
IComparer	The wrapped IComparer.

Methods

Compare(object, object)

Compares its two arguments for order.

Declaration

public virtual int Compare(object o1, object o2)

Parameters

Type	Name	Description
object	o1	The first object to be compared.
object	o2	The second object to be compared.

Returns

Type	Description
int	A negative integer, zero, or a positive integer as the first argument is less than, equal to, or greater than the second.

Remarks

Returns a negative integer, zero, or a positive integer as the first argument is less than, equal to, or greater than the second. null values are evaluated as "less then" any non-null value. If the wrapped comparer is not specified, all non-null values must implement the IComparable interface.

Exceptions

Type	Condition
InvalidCastException	If the arguments' types prevent them from being compared by this IComparer.

CompareEntries(IQueryCacheEntry, IQueryCacheEntry)

Compare two entries based on the rules specified by IComparer.

Declaration

public virtual int CompareEntries(IQueryCacheEntry entry1, IQueryCacheEntry entry2)

Parameters

Type	Name	Description
IQueryCacheEntry	entry1	The first entry to compare values from; read-only.
IQueryCacheEntry	entry2	The second entry to compare values from; read-only.

Returns

Type	Description
int	A negative integer, zero, or a positive integer as the first entry denotes a value that is is less than, equal to, or greater than the value denoted by the second entry .

Remarks

If possible, use the Extract(IValueExtractor) method to optimize the value extraction process.

This method is expected to be implemented by IComparer wrappers, which simply pass on this invocation to the wrapped IComparer objects if they too implement this interface, or to invoke their default compare method passing the actual objects (not the extracted values) obtained from the extractor using the passed entries.

This interface is also expected to be implemented by IValueExtractor implementations that implement the IComparer interface. It is expected that in most cases, the IComparer wrappers will eventually terminate at (i.e. delegate to) IValueExtractors that also implement this interface.

Exceptions

Type	Condition
InvalidCastException	If the arguments' types prevent them from being compared by this IComparer.
ArgumentException	If the extractor cannot handle the passed objects for any other reason; an implementor should include a descriptive message.

CompareSafe(IComparer, object, object)

Compares its two arguments for order.

Declaration

public static int CompareSafe(IComparer comparer, object o1, object o2)

Parameters

Type	Name	Description
IComparer	comparer	A comparer to use for the comparison (optional).
object	o1	The first object to be compared.
object	o2	The second object to be compared.

Returns

Type	Description
int	A negative integer, zero, or a positive integer as the first argument is less than, equal to, or greater than the second.

Remarks

Returns a negative integer, zero, or a positive integer as the first argument is less than, equal to, or greater than the second. Null values are evaluated as "less then" any non-null value. Non-null values that do not implement IComparable interface will be evaluated as equal.

Exceptions

Type	Condition
ArgumentException	If the arguments are not of the same type or do not implement IComparable.

Equals(object)

Determine if two comparers are equal.

Declaration

public override bool Equals(object o)

Parameters

Type	Name	Description
object	o	The other comparer.

Returns

Type	Description
bool	true if the passed object is equal to this.

Overrides

object.Equals(object)

GetHashCode()

Return the hash code for this comparator.

Declaration

public override int GetHashCode()

Returns

Type	Description
int	The hash code value for this comparator.

Overrides

object.GetHashCode()

IsKeyComparer()

Specifies whether this comparer expects to compare keys or values.

Declaration

public bool IsKeyComparer()

Returns

Type	Description
bool	true if entry keys are expected; false otherwise.

IsKeyComparer(IComparer)

Check whether the specified comparer expects to compare keys or values.

Declaration

public static bool IsKeyComparer(IComparer comparer)

Parameters

Type	Name	Description
IComparer	comparer	A IComparer to check.

Returns

Type	Description
bool	true if the comparer expects keys; false otherwise.

ReadExternal(IPofReader)

Restore the contents of a user type instance by reading its state using the specified IPofReader object.

Declaration

public virtual void ReadExternal(IPofReader reader)

Parameters

Type	Name	Description
IPofReader	reader	The IPofReader from which to read the object's state.

Exceptions

Type	Condition
IOException	If an I/O error occurs.

ToString()

Returns a human-readable description for this IComparer.

Declaration

public override string ToString()

Returns

Type	Description
string	A string description of the IComparer.

Overrides

object.ToString()

WriteExternal(IPofWriter)

Save the contents of a POF user type instance by writing its state using the specified IPofWriter object.

Declaration

public virtual void WriteExternal(IPofWriter writer)

Parameters

Type	Name	Description
IPofWriter	writer	The IPofWriter to which to write the object's state.

Exceptions

Type	Condition
IOException	If an I/O error occurs.

Implements

IQueryCacheComparer

IEntryAwareComparer

IComparer

IPortableObject