bdlb_printadapter

Detailed Description

Outline

• Purpose
• Classes
• Description
  • Usage
    • Example 1: Use in C++03
    • Example 2: Use of PrintAdapterUtil::makeAdapter
    • Example 3: Use in C++17 With CTAD

Purpose

Provide object for streaming objects using bdlb::PrintMethods.

Classes

• bdlb::PrintAdapter: class for streaming objects using bdlb::PrintMethods.
• bdlb::PrintAdapterUtil: utility for constructing bdlb::PrintAdapter.

Description

This component provides a template class that will enable any object that can be streamed using bdlb::PrintMethods to be streamed via <<.

Through using this class, one can stream an object using operator<< and at the same time specify level and spacesPerLevel arguments to appropriately indent and format the output.

Usage

This section illustrates intended use of this component.

Example 1: Use in C++03

Suppose we have a few bdlb::IdentSpan objects that we want to print, only we want to stream them with operator<< and we want to specify non-default values of level and spacesPerLevel to their streaming.

const bdlb::IndexSpan a(3, 7), b(241, 22), c(23, 17);

First, we create a typedef of 'PrintAdapter<IdentSpan>' to use:

typedef bdlb::PrintAdapter<bdlb::IndexSpan> PAIS;

Then, we create a line of dashes:

const char * const line = "------------------------------------"
                          "------------------------------------\n";

Now, we use the typedef to construct temporary PrintAdapter objects to stream our IndexSpan objects:

cout << "    a: " << line << PAIS(&a, 2, 2)
     << "    b: " << line << PAIS(&b, 3, 2)
     << "    c: " << line << PAIS(&c, 4, 2);

Finally, we see the output:

 a: ------------------------------------------------------------------------
 [
   position = 3
   length = 7
 ]
 b: ------------------------------------------------------------------------
   [
     position = 241
     length = 22
   ]
 c: ------------------------------------------------------------------------
     [
       position = 23
       length = 17
     ]

Example 2: Use of PrintAdapterUtil::makeAdapter

Suppose we have a few bdlb::IdentSpan objects that we want to print, only we want to stream them with operator<< and we want to specify non-default values of level and spacesPerLevel to their streaming.

const bdlb::IndexSpan a(3, 7), b(241, 22), c(23, 17);

First, we make a typedef to the namespace struct:

typedef bdlb::PrintAdapterUtil Util;

Then, we create a line of dashes:

const char * const line = "------------------------------------"
                          "------------------------------------\n";

Now, we call the static function PrintAdapterUtil::makeAdapter on the IndexSpan objects to stream which will return streamable PrintAdapter objects:

cout << "    a: " << line << Util::makeAdapter(a, 2, 2)
     << "    b: " << line << Util::makeAdapter(b, 3, 2)
     << "    c: " << line << Util::makeAdapter(c, 4, 2);

Finally, we see the output:

 a: ------------------------------------------------------------------------
 [
   position = 3
   length = 7
 ]
 b: ------------------------------------------------------------------------
   [
     position = 241
     length = 22
   ]
 c: ------------------------------------------------------------------------
     [
       position = 23
       length = 17
     ]

Example 3: Use in C++17 With CTAD

Suppose you have a few bdlb::IdentSpan objects that you want to print, only you want to stream them with operator<< and you want to specify non-default values of level and spacesPerLevel to their streaming.

const bdlb::IndexSpan a(3, 7), b(241, 22), c(23, 17);

First, we create a line of dashes:

const char * const line = "------------------------------------"
                          "------------------------------------\n";

Now, you call the constructor PrintAdapter on the IndexSpan objects to stream and CTAD will create the right template specification:

cout << "    a: " << line << bdlb::PrintAdapter(&a, 2, 2)
     << "    b: " << line << bdlb::PrintAdapter(&b, 3, 2)
     << "    c: " << line << bdlb::PrintAdapter(&c, 4, 2);

Finally, we see the output:

 a: ------------------------------------------------------------------------
 [
   position = 3
   length = 7
 ]
 b: ------------------------------------------------------------------------
   [
     position = 241
     length = 22
   ]
 c: ------------------------------------------------------------------------
     [
       position = 23
       length = 17
     ]