Convenience class that simply stores a Logger and/or Component passed into a constructor; and returns this Logger and Component via get_logger() and get_log_component() public accessors. More...

#include <log.hpp>

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Public Member Functions
	Log_context (Logger *logger=0)
	Constructs Log_context by storing the given pointer to a Logger and a null Component. More...

template<typename Component_payload >
	Log_context (Logger *logger, Component_payload component_payload)
	Constructs Log_context by storing the given pointer to a Logger and a new Component storing the specified generically typed payload (an `enum` value). More...

	Log_context (const Log_context &src)
	Copy constructor that stores equal `Logger*` and Component values as the source. More...

	Log_context (Log_context &&src)
	Move constructor that makes this equal to `src`, while the latter becomes as-if default-constructed. More...

Log_context &	operator= (const Log_context &src)
	Assignment operator that behaves similarly to the copy constructor. More...

Log_context &	operator= (Log_context &&src)
	Move assignment operator that behaves similarly to the move constructor. More...

void	swap (Log_context &other)
	Swaps Logger pointers and Component objects held by `*this` and `other`. More...

Logger *	get_logger () const
	Returns the stored Logger pointer, particularly as many `FLOW_LOG_*()` macros expect. More...

const Component &	get_log_component () const
	Returns reference to the stored Component object, particularly as many `FLOW_LOG_*()` macros expect. More...

Private Attributes
Logger *	m_logger
	The held Logger pointer. Making the pointer itself non-`const` to allow `operator=()` to work. More...

Component	m_component
	The held Component object. Making the object non-`const` to allow `operator=()` to work. More...

Detailed Description

Convenience class that simply stores a Logger and/or Component passed into a constructor; and returns this Logger and Component via get_logger() and get_log_component() public accessors.

It's extremely useful (almost mandatory in conventional practice) for classes that want to log, as they can simply derive from it (passing in the desired Logger* and Component payload (an enum value) into the Log_context superclass constructor), at which point the get_logger() and get_log_component() functions the FLOW_LOG_...() macros expect automatically become available without any additional code having to be written in the logging class. Here is how:

class I_like_to_have_fun_and_log_about_it :
  public flow::log::Log_context
{
public:
  I_like_to_have_fun_and_log_about_it() :
    // Glue FLOW_LOG_*() macros to the following simple logger and component FUN_HAVER.
    Log_context(&m_logger, My_cool_components::S_FUN_HAVER),
    // Initialize stdout logger that logs INFO-or-higher-severity messages.
    m_logger(true, std::cout, std::cout, flow::log::Sev::S_INFO),
    // ... other initializers and superclass constructors, if any ...
  {
    FLOW_LOG_INFO("I can log right from the constructor and throughout *this lifetime!");
    // ... other code ...
  }
 
private:
  void do_fun_stuff()
  {
    // This macro works, because Log_context superclass defines get_logger() which returns m_logger,
    // and component() returns My_cool_components::S_FUN_HAVER.
    // But we need not ever worry about such details.
    FLOW_LOG_INFO("I am about to do something cool and fun: " << 42 << "!");
    // ... more code ...
  }
 
  // I will use a simple stdout/stderr logger for my logging. It's passed to Log_context in constructor.
  flow::log::Simple_ostream_logger m_logger;
}; // class I_like_to_have_fun_and_log_about_it

Note that the operator=() allows one to change the underlying Logger anytime after construction (e.g., existing_log_context = Log_context(&some_logger, Some_enum::S_SOME_COMPONENT);).

Implementation notes

The code could be shorter by getting rid of non-copy constuctor in favor of direct member initialization by user; and by simply omitting the API for the auto-generated copy constructor and assignment. However, in this case, I wanted to clearly document the API; and since there are more than 1 constructors, it seemed better to explicitly declare them all instead of replacing some with implicitly required direct initialization (again to make API more clearly documented).

Thread safety

The only operation of interest w/r/t threads is the aforementioned implicit assignment operator. Thread safety is the same as for any struct with no locking done therein.

Definition at line 1618 of file log.hpp.

Constructor & Destructor Documentation

◆ Log_context() [1/4]

flow::log::Log_context::Log_context ( Logger * logger = 0 )

explicit

Constructs Log_context by storing the given pointer to a Logger and a null Component.

Parameters

logger Pointer to store. Rationale for providing the null default: To facilitate subclass = default no-arg ctors.

Definition at line 195 of file log.cpp.

◆ Log_context() [2/4]

template<typename Component_payload >

flow::log::Log_context::Log_context	(	Logger *	logger,
		Component_payload	component_payload
	)

explicit

Constructs Log_context by storing the given pointer to a Logger and a new Component storing the specified generically typed payload (an enum value).

For more background on Component see its doc header.

Template Parameters

Component_payload See Component constructor doc header: Payload template arg specifically.

Parameters

logger	Pointer to store.
component_payload	See Component constructor doc header: `payload` arg specifically.

Definition at line 1758 of file log.hpp.

◆ Log_context() [3/4]

flow::log::Log_context::Log_context ( const Log_context & src )

explicitdefault

Copy constructor that stores equal Logger* and Component values as the source.

This is explicit, even though an unintentional copy (e.g., in a bind sans cref or ref) would just internally involve the copying a pointer (as of this writing). The reason is that it's unlikely one wants to blithely copy these objects or objects of a sub-type; most likely (at least in scenarios seen so far, as of this writing) a cref or ref is in order instead. (I am open to counter-examples and thus removing this explicit keyword if convinced by one.)

Parameters

src	Source object.

◆ Log_context() [4/4]

flow::log::Log_context::Log_context ( Log_context && src )

Move constructor that makes this equal to src, while the latter becomes as-if default-constructed.

Parameters

src	Source object.

Definition at line 203 of file log.cpp.

References operator=().

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Member Function Documentation

◆ get_log_component()

const Component & flow::log::Log_context::get_log_component ( ) const

Returns reference to the stored Component object, particularly as many FLOW_LOG_*() macros expect.

Note: It's public at least so that FLOW_LOG_SET_CONTEXT() works in all reasonable contexts.

Returns: See above.

Definition at line 229 of file log.cpp.

References m_component.

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◆ get_logger()

Logger * flow::log::Log_context::get_logger ( ) const

Returns the stored Logger pointer, particularly as many FLOW_LOG_*() macros expect.

Note: It's public at least so that FLOW_LOG_SET_CONTEXT() works in all reasonable contexts.

Returns: See above.

Definition at line 224 of file log.cpp.

References m_logger.

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◆ operator=() [1/2]

Log_context & flow::log::Log_context::operator= ( const Log_context & src )

default

Assignment operator that behaves similarly to the copy constructor.

Parameters

src	Source object.

Returns: *this.

Referenced by Log_context().

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◆ operator=() [2/2]

Log_context & flow::log::Log_context::operator= ( Log_context && src )

Move assignment operator that behaves similarly to the move constructor.

Parameters

src	Source object.

Returns: *this.

Definition at line 210 of file log.cpp.

References m_component, m_logger, swap(), and flow::log::swap().

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◆ swap()

void flow::log::Log_context::swap ( Log_context & other )

Swaps Logger pointers and Component objects held by *this and other.

No-op if this == &other.

Parameters

other Other object.

Definition at line 234 of file log.cpp.

References m_component, m_logger, swap(), and flow::log::swap().

Referenced by operator=(), swap(), and flow::log::swap().

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Member Data Documentation

◆ m_component

Component flow::log::Log_context::m_component

private

The held Component object. Making the object non-const to allow operator=() to work.

Definition at line 1721 of file log.hpp.

Referenced by get_log_component(), operator=(), and swap().

◆ m_logger

Logger* flow::log::Log_context::m_logger

private

The held Logger pointer. Making the pointer itself non-const to allow operator=() to work.

Definition at line 1719 of file log.hpp.

Referenced by get_logger(), operator=(), and swap().

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

log/log.hpp
log/log.cpp

Public Member Functions

Private Attributes

Detailed Description

Implementation notes

Thread safety

Constructor & Destructor Documentation

◆ Log_context() [1/4]

◆ Log_context() [2/4]

◆ Log_context() [3/4]

◆ Log_context() [4/4]

Member Function Documentation

◆ get_log_component()

◆ get_logger()

◆ operator=() [1/2]

◆ operator=() [2/2]

◆ swap()

Member Data Documentation

◆ m_component

◆ m_logger