NAME

Module::Generic::Scalar - String Manipulation Object Class

SYNOPSIS

    my $s = Module::Generic::Scalar->new( "John Doe" );
    print( $s->substr( 0, 4 ), "\n" );
    # prints: John

VERSION

    v1.1.0

DESCRIPTION

The purpos of this calss/package is to provide an object-oriented approach to string manipulation.

The object is overloaded, so it returns the embedded string when used as a string.

    print( "I met with $s\n" );

Would produce: I met with John Doe

METHODS

new

Provided with scalar reference, an array or just a regular string and this returns a new object.

If an array reference or an array-based object is provided like Module::Generic::Array, this will concatenate all the array elements

append

Provided with a string, and this will add it to the end of the string object.

    # $s is 'Hello'
    $s->append( ' world' );
    # now this is: Hello world

as_array

Returns the current string value as an Module::Generic::Array object.

as_boolean

Returns a Module::Generic::Boolean object with its value set to true or false based on the value of the scalar object.

    # $s is 1
    $s->as_boolean; # sets to true
    # $s is 0
    $s->as_boolean; # sets to false
    # $s is hello
    $s->as_boolean: # sets to true
    # $s is undefined or empty
    $s->as_boolean: # sets to false
    # etc...

Module::Generic::Boolean objects are very useful because they can be used in perl as o or 1 to indicate false or true, but when used in json, they are automatically converted to false or true

as_number

    Returns the current string as an L<Module::Generic::Number> object.

as_string

Returns the object string as a string.

    my $s = Module::Generic::Scalar->new( "Mary Jane" );
    print( "Hello $s\n" );
    # Hello Mary Jane

callback

Sets or gets a callback on the scalar object. You can set 2 types of callback: add or remove which will be called respectively when you add something to the scalar or when you remove something from it.

It does this by tieing the scalar to its internal class Module::Generic::Scalar::Tie that will call the add or remove callback when data is being added or removed, no matter how, i.e. be it through the methods of this class, or by directly trying to add data to it:

    my $str = Module::Generic::Scalar->new();
    $a->callback( add => sub
    {
        my( $new ) = @_;
        return unless( $$new eq $approved_string );
        return(1);
    });
    $str->append( $some_string );
    # or
    $str .= $some_string;

In both cases above the string will be added, and if it were some other unapproved text, the data would not be added to the string.

So, the callback must return true to allow the data to be added, or undef to refuse. Returning an empty string or 0 will not work to be considered a rejection even though it is a false value.

Both add and remove callbacks receives an hash reference as its sole arguments.

The add callback receives an hash reference with the following properties:

added

A scalar reference to the new value being set in replacement of the old one, so you can inspect it.

removed

A scalar reference to the old value being replaced, so you can inspect it.

type

The callback type: add

The remove callback works the same way, but for any operation that tries to remove data from the string. It receives an hash reference with the following properties:

removed
type

The callback type: remove

    my $str = Module::Generic::Scalar->new();
    $str->callback( remove => sub
    {
        my( $old, $new ) = @_;
        # Do some check to accept or reject
        return(1); # always return true to accept
    });
    $str->substr( 3, 4, $some_other_text ); # Attempt to change the string

This example above would call the callback passing it the old and new string.

To replace a callback, simply add another one. It will replace the previous one.

You can get the callback code associated with a callback by calling callback with one argument: the callback type.

    my $code_ref = $str->callback( 'add' );

To remove a callback, pass undef:

    $str->callback( add => undef );
    $str->callback( remove => undef );

By default, a scalar object is not tied to Module::Generic::Scalar::Tie and no callback are set nor used. Be mindful when using callbacks since it will slow things down a little bit even though it is s very thin layer.

See perltie for more information on tieing data.

capitalise

Returns a new Module::Generic::Scalar object representing the string with the words capitalised, done in a smart way. That is the special words like and, but, if, on, or, the, to, etc. are not capitalised.

This is based on the work done by John Gruber and Aristotle Pagaltzis

chomp

Just like "chomp" in perlfunc, this removes the trailing new lines in the string object, if any.

As per the perl documentation for "chomp" in perlfunc, "it returns the total number of characters removed from all its arguments."

chop

Just like "chop" in perlfunc, this removes the trailing character in the string object, no matter what it is, and returns the character chopped.

clone

Returns a copy of the object.

crypt

This takes a "salt" and returns an encrypted version of the string. See "crypt" in perlfunc. Note that this does not work well on some BSD systems.

defined

Returns true or false whether the string object contains a defined string, i.e. not undef

empty

Alias for "reset". This empties the scalar object, making it zero-byte in length.

fc

Just like "fc" in perlfunc, provided with a string, this enables comparison with casefolding.

To quote from the manual: "Casefolding is the process of mapping strings to a form where case differences are erased".

    lc($this) eq lc($that)    # Wrong!
    # or
    uc($this) eq uc($that)    # Also wrong!
    # or
    $this =~ /^\Q$that\E\z/i  # Right!
    # And now
    my $s = Module::Generic::Scalar( $this );
    $s->fc( $that );

hex

Returns the hex value of the string.

index

Given a sub string and an optional position, and this returns the position at which the sub string was found. as a Module::Generic::Number object.

See "index" in perlfunc

is_alpha

Returns true if the string contains only alphabetic characters, or else it returns false.

This uses perl's [[:alpha:]] to test.

is_alpha_numeric

Returns true if the string contains only alphabetic or numeric characters, or else it returns false.

This uses perl's [[:alnum:]] to test.

is_empty

Returns true if the string is zero in length, or else it returns false.

is_lower

Returns true if the string contains only lower case characters, or else it returns false.

This uses perl's [[:lower:]] to test.

is_numeric

Returns true if the string contains only numeric characters, or else it returns false.

This uses "looks_like_number" in Scalar::Util

is_upper

Returns true if the string contains only upper case characters, or else it returns false.

This uses perl's [[:upper:]] to test.

join

Takes a string as the delimiter and one or more elements and this will join the current string object and the other string elements provided using the string delimiter. For example:

    my $s = Module::Generic::Scalar->new( 'Jack John Paul Peter' );
    # Takes the string, split it by space (now an array), join it by comma (now a scalar) and rejoin it with more strings
    say $s->split( qr/[[:blank:]]+/ )->join( ', ' )->join( ', ', qw( Gabriel Raphael Emmanuel ) );
    # prints: Jack, John, Paul, Peter, Gabriel, Raphael, Emmanuel

Note that if, among the element passed to "join", an aray object is provided, it will not be expanded. Thus, if you do something like this:

    my $a = Module::Generic::Array->new( [qw( John Peter )] );
    say Module::Generic::Scalar->new( 'Paul' )->join( ', ', $a );

It wil lnot produce Paul, John, Peter, but instead something like: Paul, Module::Generic::Array=ARRAY(0x5646f0116470)

That's because there is no way to guess if the user wanted to pass on a list or just an object and making that kind of assumption is dangerous.

What you woud want to do instead is:

    say Module::Generic::Scalar->new( 'Paul' )->join( ', ', $a->list );

Or maybe

    say Module::Generic::Scalar->new( 'Paul' )->join( ', ', @$a );

Of course, passing an overloaded object that has the stringification capability will transform it automatically into a string before being joined. Thus:

    my $word1 = Module::Generic::Scalar->new( 'Hello' );
    my $word2 = Module::Generic::Scalar->new( 'world' );
    say $word1->join( ' ', $word2 );

will yield: Hello world because Module::Generic::Scalar objects have overloaded stringification capability.

It returns the newly formed string as a new Module::Generic::Scalar object.

lc

Takes the current string object and returns a new Module::Generic::Scalar object with the string all in lower case.

lcfirst

Takes the current string object and returns a new Module::Generic::Scalar object with the first character of the string in lower case.

left

Provided with a number and this will get the chunk starting from the left of the string object.

    Module::Generic::Scalar->new( "Hello world" )->left( 5 );
    # will produce: Hello

See also "right"

length

This returns the length of the string, as a Module::Generic::Number object.

like

Provided with a string or a regular express and this return the value of the regular expression evaluation against the object string.

    my $s = "I disapprove of what you say, but I will defend to the death your right to say it";
    print( "Matches? ", $s->like( qr/\bapprove[[:blank:]\h]+what\b/ ) ? 'yes' : 'no', "\n" ); # print yes

If there is no match, it returns 0, but in object, list or scalar context or when there are matches, it returns a Module::Generic::RegexpCapture object. This object stringifies into the number of matches, so you can do:

    if( $s->like( qr/[[:blank:]\h]+/ ) )
    {
        # Do something
    }

or

    if( my $rv = $s->like( qr/([[:blank:]\h]+)/ )->result )
    {
        my $first_match = $rv->capture->first;
        # Do something
    }

See also "match" and "replace"

lower

Alias for "lc"

ltrim

This removes any new line and space characters, i.e. \r and \n at the begining of the string.

It takes an optional argument that can be an alternative string to remove at the end of the sstring or a regular expression, such as one provided with "perlfunc/qr"

    $s->ltrim( qr/[[:blank:]\h]+/ ); # Remove all kind of leading whitespaces

It returns the object itself for chaining.

See also "rtrim"

match

Provided with a string or a regular expression like the one created with "qr" in perlfunc and this returns true or false whether the string object matched or not.

    # $s is "Hello world"
    $s->match( 'world' ); # pass
    $s->match( qr/WORLD/i ); # pass
    $s->match( 'monde' ); # obviously fail

If there is no match, it returns 0, but in object, list or scalar context or when there are matches, it returns a Module::Generic::RegexpCapture object. This object stringifies into the number of matches, so you can do:

    if( $s->match( qr/[[:blank:]\h]+/ ) )
    {
        # Do something
    }

or

    if( my $rv = $s->match( qr/([[:blank:]\h]+)/ )->result )
    {
        my $first_match = $rv->capture->first;
        # Do something
    }

See also "like" and "replace"

object

Returns the current object. This is useful when chaining to force an object context. For example, with "unpack". In scalar context, "unpack", as per the "unpack" in perlfunc documentation will return the first element:

    my $unpack = $unpack_data->unpack( "A10xA28xA8A*" );

But what if we wanted $unpack to not be the first element, but the array object? For that, we would need to call "unpack" in object context:

    my $unpack = $unpack_data->unpack( "A10xA28xA8A*" )->object;

open

Opens the scalar in read/write mode and returns an object with same capabilities as regular file handle.

ord

This returns the value of "ord" in perlfunc on the string, as a Module::Generic::Number object.

pack

Like "pack" in perlfunc, this takes a template and convert the string object. "The resulting string is the concatenation of the converted values."

It returns a new Module::Generic::Scalar object.

See also "pack" in Module::Generic::Array

pad

Provided with a number n and a string and this will create n instance of the string. If the number is positive, the string will be placed at the begining and if negative, it will be placed at the end

    $s->pad( 3, 'X' );
    # XXXHello world

    $s->padd( -3, 'X' );
    # Hello worldXXX

pos

This sets or gets the position inside the string object. See "pos" in perlfunc for detail about this.

prepend

Takes some data as its unique argument and prepend it to the scalar object underlying value.

If you want to pass multiple data, you will have to join them first:

    $s->prepend( join( '', qw( Cogito ergo sum ) ) );

quotemeta

Given a string, this return a new Module::Generic::Scalar object with the given string characters escapeed with "quotemeta" in perlfunc.

replace

Provided with a string or a regular expression and a replacement string and this will replace all instance of the string or regular expression with the replacement string provided.

    # $s is Hello world
    my $rv = $s->replace( ' ', '_' ); # Hello_world
    my $rv = $s->replace( qr/[[:blank:]\h]+/, '_' ); # Hello_world

If there is no match, it returns 0, but in object, list or scalar context or when there are matches, it returns a Module::Generic::RegexpCapture object. This object stringifies into the number of matches, so you can do:

    if( $s->replace( qr/[[:blank:]\h]+/, '_' ) )
    {
        # Do something
    }

or

    if( my $rv = $s->replace( qr/([[:blank:]\h]+)/, '_' )->result )
    {
        my $first_match = $rv->capture->first;
        # Do something
    }

See also "like" and "match"

reset

This empty the string inside the object.

reverse

Given a string, this return a new Module::Generic::Scalar object with the given string cin reverse order.

Provided with a number and this will get the chunk starting from the right of the string object.

    Module::Generic::Scalar->new( "Hello world" )->right( 5 );
    # will produce: world

See also "left"

rindex

Given a sub string and an optional position, and this returns the position at which the sub string was found, starting from the end.

See "rindex" in perlfunc

rtrim

This removes any new line and space characters, i.e. \r and \n at the end of the string.

It takes an optional argument that can be an alternative string to remove at the end of the sstring or a regular expression, such as one provided with "perlfunc/qr"

    $s->rtrim( qr/[[:blank:]\h]+/ ); # Remove all kind of trailing whitespaces

It returns the object itself for chaining.

See also "ltrim"

scalar

Returns the string within this scalar object. This calls "as_string"

set

Provided with a scalar reference or scalar-based object like Module::Generic::Scalar or an array reference and this sets the current string/.

This acts the exact same way as for "new", except it acts on the current object string.

split

Provided with a string or an expression and this returns the list in list context or, in scalar context, an array reference as an Module::Generic::Array object.

Be careful that you cannot just do like perl's original split such as:

    my $a = $s->split( /\n/ );

Because /\n/ is not passed as an argument, i.e. it results in no argument being passed, so you do need to either provide the expression as "\n" or as a regular expression:

    my $a = $s->split( qr/\n/ );

It will warn you if no argument was provided.

sprintf

Provided with a list of arguments, and this replace the placeholders just like "sprintf" in perlfunc does.

substr

Provided with an offset, an optional length and an optional replacement string, and this return a new Module::Generic::Scalar object.

See "substr" in perlfunc for more information.

tr

Provided with a search list and a replacement list and this will perform just like the perl core "tr" in perlfunc function.

It also accepts options like cdsr and returns the resulting value.

trim

Provided with a target string or a regular expression, and this will remove any occurence of them in the string object.

uc

Takes the current string object and returns a new Module::Generic::Scalar object with the string all in upper case.

ucfirst

Takes the current string object and returns a new Module::Generic::Scalar object with the first character of the string in upper case.

undef

Sets the underlying string object to undef.

This would make

    print( $s->defined ? 'defined' : 'undefined', "\n" );

return false, but becareful that you cannot do:

    print( $s ? 'defined' : 'undefined', "\n" );

Because $s is the object so it would always return true.

If you stringify it like

    print( "$s" ? 'defined' : 'undefined', "\n" );

It would still return as defined, because this would be a defined string, albeit empty

unpack

    my $array = $s->unpack( "W" );
    # Returns the ord() value as a Module::Generic::Array object
    $s->unpack( "W" )->length;
    # Object context. Ditto
    my( $date, $desc, $income, $expend ) = $s->unpack( "A10xA27xA7A*" );
    # Returns a regular list of values

Does the reverse of "pack". Provided with a template, it takes the string object and expands it out into a list of values.

It returns an Module::Generic::Array object in object or scalar context, and a regular list in list context.

upper

Alias for "uc"

SEE ALSO

Module::Generic::Number, Module::Generic::Array, Module::Generic::Boolean, Module::Generic::Hash, Module::Generic::Dynamic

AUTHOR

Jacques Deguest <jack@deguest.jp>

COPYRIGHT & LICENSE

Copyright (c) 2000-2020 DEGUEST Pte. Ltd.

You can use, copy, modify and redistribute this package and associated files under the same terms as Perl itself.