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cpp/io/basic stringstream/str: differenze tra le versioni

Da cppreference.com.
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Riga 1: Riga 1:
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{{title|str}}
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{{|str}}
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Sintassi:
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<syntaxhighlight lang="cpp">
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cpp/str
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    #include <sstream>
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:cpp/str
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    void str( const string& s );
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:cpp/stringstreamstr
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    string str();
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:cpp//str
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</syntaxhighlight>
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:///str
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:///
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La funzione str() può essere usata in due modi: il primo per avere una copia della stringa che viene manipolata
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[[cpp/io//]]
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all'interno dello stream:
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[[cpp/io/]]
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<syntaxhighlight lang="cpp">
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    ostringstream stream1;
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    stream1 << "Testing!" << endl;
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    cout << stream1.str();
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</syntaxhighlight>
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Nel secondo str() può essere usata per copiare una stringa dentro lo stream. Questo metodo è utile soprattutto
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con gli input streams. Esempio:
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<syntaxhighlight lang="cpp">
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    istringstream stream1;
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    string string1 = "25";
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    stream1.str(string1);
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</syntaxhighlight>
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N.B.: Questa funzione lascia i puntatori "get" e "put" impostati a 0.
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Questo talvolta conduce a risultati confondenti quando si inizializza una
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stringstream per operazioni bidirezionali.
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str() è utile anche quando è necessario azzerare lo strem cosicchè possa essere riutilizzato.
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__Attenzione__: la funzione membro ''clear()'' **non** cancella i
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contenuti dell'oggetto stringa contenuto nello stream, semplicemente
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si limita ad effettuare il clear dello stato dell'oggetto ios, cioè esegue la funzione equivalente di
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basic_ios::clear().
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<syntaxhighlight lang="cpp">
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    istringstream stream1;
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    float num;
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    // use it once
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    string string1 = "25 1 3.235\n1111111\n222222";
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    stream1.str(string1);
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    while( stream1 >> num ) cout << "num: " << num << endl;  // displays numbers, one per line
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    // use the same string stream again with str()
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    string string2 = "1 2 3 4 5  6 7 8 9 10";
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    stream1.clear(); // not what you think!  But still required to clear the stream's IO state
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    stream1.str(string2);
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    while( stream1 >> num ) cout << "num: " << num << endl;  // displays numbers, one per line
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</syntaxhighlight>
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Argomenti collegati: [[cpp/io/basic_stringstream/rdbuf | rdbuf]], [[cpp/io | C++ I/O Streams]]
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Versione attuale delle 13:32, 2 lug 2013

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C++
 
Ingresso / libreria di output
I / O manipolatori
C-style I / O
Buffer
Original:
Buffers
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basic_streambuf
basic_filebuf
basic_stringbuf
strstreambuf(deprecato)
Streams
Original:
Streams
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Astrazioni
Original:
Abstractions
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ios_base
basic_ios
basic_istream
basic_ostream
basic_iostream
File I / O
Original:
File I/O
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basic_ifstream
basic_ofstream
basic_fstream
String I / O
Original:
String I/O
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basic_istringstream
basic_ostringstream
basic_stringstream
Array I / O
Original:
Array I/O
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istrstream(deprecato)
ostrstream(deprecato)
strstream(deprecato)
Tipi
Original:
Types
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streamoff
streamsize
fpos
Errore categoria interfaccia
Original:
Error category interface
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iostream_category(C++11)
io_errc(C++11)
 
std::basic_stringstream
Membri funzioni
Original:
Member functions
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basic_stringstream::basic_stringstream
basic_stringstream::operator=
basic_stringstream::swap
basic_stringstream::rdbuf
String operazioni
Original:
String operations
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basic_stringstream::str
 
std::basic_string<CharT,Traits,Allocator> str() const;
 (1)
void str(const std::basic_string<CharT,Traits,Allocator>& new_str);
 (2)
Gestisce il contenuto dell'oggetto stringa sottostante.
Original:
Manages the contents of the underlying string object.
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1)
Restituisce una copia della stringa sottostante come se chiamando rdbuf()->str().
Original:
Returns a copy of the underlying string as if by calling rdbuf()->str().
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2)
Sostituisce il contenuto della stringa sottostante come se chiamando rdbuf()->str(new_str).
Original:
Replaces the contents of the underlying string as if by calling rdbuf()->str(new_str).
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Indice

[modifica] Parametri

new_str -
nuovi contenuti della stringa sottostante
Original:
new contents of the underlying string
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[modifica] Valore di ritorno

1)
una copia dell'oggetto stringa sottostante.
Original:
a copy of the underlying string object.
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2)
(Nessuno)
Original:
(none)
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[modifica] Esempio

#include <sstream>
#include <iostream>
int main()
{
    int n;
 
    std::istringstream in;  // could also use in("1 2")
    in.str("1 2");
    in >> n;
    std::cout << "after reading the first int from \"1 2\", the int is "
              << n << ", str() = \"" << in.str() << "\"\n";
 
    std::ostringstream out("1 2");
    out << 3;
    std::cout << "after writing the int '3' to output stream \"1 2\""
              << ", str() = \"" << out.str() << "\"\n";
 
    std::ostringstream ate("1 2", std::ios_base::ate);
    ate << 3;
    std::cout << "after writing the int '3' to append stream \"1 2\""
              << ", str() = \"" << ate.str() << "\"\n";
}

Output: 

after reading the first int from "1 2", the int is 1, str() = "1 2"
after writing the int '3' to output stream "1 2", str() = "3 2"
after writing the int '3' to append stream "1 2", str() = "1 23"

[modifica] Vedi anche
sostituisce o ottiene una copia della stringa di caratteri associata
Original:
replaces or obtains a copy of the associated character string
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(metodo pubblico) [modifica]
Estratto da "https://it.cppreference.com/mwiki/index.php?title=cpp/io/basic_stringstream/str&oldid=25756"