51Degrees Device Detection C/C++  4.5

A device detection library that is used natively or by 51Degrees products

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FiftyoneDegrees::Common::Value< T > Class Template Reference

Detailed Description

template<class T>
class FiftyoneDegrees::Common::Value< T >

Encapsulates a value returned an instance of ResultsBase for a specified property.

An instance contains either the value, or the reason which there is no value.

Before retrieving the value itself, its presence should first be checked using the hasValue() method. The typed value can be returned either using the getValue() method, or more simply, by dereferencing (similarly to an iterator). If there is no value, then an exception will be thrown.

Usage Example

using namespace FiftyoneDegrees::Common;

Value<string> value;

// Check that there is a valid value

if (value.hasValue()) {

// Get the value

string stringValue = *value;

// Do something with the value

// ...

}

else {

// Get the reason for the value being invalid

string message = value.getNoValueMessage();

// Do something with the message

// ...

}

// Or just try getting the value and catch the exception. Note that

// this is not the recommended method.

try {

string stringValue = *value;

}

catch (exception e) {

const char *message = e.what();

}

Template Parameters

T	the type of the value e.g. string

Examples

Hash/GettingStarted.cpp.

Public Member Functions
Constructors
	Value ()
	Default constructor.
Value Methods
bool	hasValue () const
	Indicates whether or not a valid value has been returned by the ResultsBase instance.
fiftyoneDegreesResultsNoValueReason	getNoValueReason () const
	Indicates the reason why valid values are not available.
const char *	getNoValueMessage () const
	Gets a message explaining why there is no value.
T	getValue () const
	Gets the value contained in the Value instance.
void	setValue (T targetValue)
	Set the value to be contained in the Value instance.
void	setNoValueReason (fiftyoneDegreesResultsNoValueReason reason, const char *message)
	Set the reason there is no value available.
Operators
T	operator* () const
	Gets the value contained in the Value instance.

Member Function Documentation

◆ getNoValueMessage()

template<class T>

const char * FiftyoneDegrees::Common::Value< T >::getNoValueMessage ( ) const

inline

Gets a message explaining why there is no value.

Calling this if hasValue() returned true will result in undefined behavior.

Returns

message explaining the reason for the missing value

Examples

Hash/GettingStarted.cpp.

◆ getNoValueReason()

template<class T>

fiftyoneDegreesResultsNoValueReason FiftyoneDegrees::Common::Value< T >::getNoValueReason ( ) const

inline

Indicates the reason why valid values are not available.

This can be called if hasValue() returns false. For a more detailed message, call getNoValueMessage().

Returns

enum indicating the reason for no valid values

◆ getValue()

template<class T>

T FiftyoneDegrees::Common::Value< T >::getValue ( ) const

inline

Gets the value contained in the Value instance.

If there is no valid value, then an exception will be thrown. To prevent an exception, the hasValue() method should be checked first.

Returns

value

Examples

Hash/GettingStarted.cpp.

◆ hasValue()

template<class T>

bool FiftyoneDegrees::Common::Value< T >::hasValue ( ) const

inline

Indicates whether or not a valid value has been returned by the ResultsBase instance.

Returns

true if there is a valid value

Examples

Hash/GettingStarted.cpp.

◆ operator*()

template<class T>

T FiftyoneDegrees::Common::Value< T >::operator* ( ) const

inline

Gets the value contained in the Value instance.

If there is no valid value, then an exception will be thrown. To prevent an exception, the hasValue() method should be checked first.

Returns

value

◆ setNoValueReason()

template<class T>

void FiftyoneDegrees::Common::Value< T >::setNoValueReason ( fiftyoneDegreesResultsNoValueReason reason, const char * message )

inline

Set the reason there is no value available.

This will be used if an exception is thrown by the setValue method.

Parameters

reason	the reason enum indicating why the value is missing
message	the message containing a fuller description on why the value is missing

◆ setValue()

template<class T>

void FiftyoneDegrees::Common::Value< T >::setValue ( T targetValue )

inline

Set the value to be contained in the Value instance.

Parameters

targetValue

the value to set

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The documentation for this class was generated from the following file:

• Value.hpp

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