sstream輸入輸出類繼承自iostream類
. istringstream讀取一個字符串
. ostringstream寫入一個字符串

1. 可以使用iostream類的操作

sstream strm; //一個未綁定的stringstream sstream strm(s); //strm持有一個string s，這個構造函數是explicit strm.str(); //返回一個string的copy strm.str(s); //將string復制進strm，返回void

stringstream構造函數會特別消耗內存，似乎不打算主動釋放內存(或許是為了提高效率)，但如果你要在程序中用同一個流，反復讀寫大量的數據，將會造成大量的內存消耗適時地清除一下緩沖 (用 stream.str("") )。

2. 字符串變基本數據類型

/字符串 變 double/
void static ioString1()
{
double n;
string str = “12.5”;
stringstream stream;
stream << str;
stream >> n;
cout << " " << n;
}
3. istringstream

void static ioString2(){istringstream istr;string line, str;while (getline(cin, line))//從終端接收一行字符串，并放入字符串line中 {istr.str(line);//把line中的字符串存入字符串流中 while (istr >> str)//每次讀取一個單詞（以空格為界），存入str中 {cout << str << endl;}} }

4. ostringstream

void static ioString3(){//初始化輸出字符串流ostr ostringstream ostr("1234");cout << ostr.str() << endl;//輸出1234 ostr.put('5');//字符4頂替了1的位置 cout << ostr.str() << endl;//輸出5234 ostr << "67";//字符串67替代了23的位置，輸出5674 string str = ostr.str();cout << str << endl;}

4. istringstream + ostringstream :

struct PersonInfo {string name;vector<string> phones;};// we'll see how to reformat phone numbers in chapter 17// for now just return the string we're givenstatic string format(const string& s) { return s; }vector<PersonInfo> static getData(istream& is){// will hold a line and word from input, respectivelystring line, word;// will hold all the records from the inputvector<PersonInfo> people;// read the input a line at a time until end-of-file (or other error)while (getline(is, line)) {if (line.length() < 2)break;PersonInfo info; // object to hold this record's dataistringstream record(line); // bind record to the line we just readrecord >> info.name; // read the namewhile (record >> word) // read the phone numbers info.phones.push_back(word); // and store thempeople.push_back(info); // append this record to people}return people;}static ostream& processOS(ostream& os, vector<PersonInfo> people){for (const auto& entry : people) { // for each entry in peopleostringstream formatted, badNums; // objects created on each loopfor (const auto& nums : entry.phones) { // for each number // ``writes'' to formatted's stringformatted << " " << format(nums);}if (badNums.str().empty()) // there were no bad numbersos << entry.name << " " // print the name << formatted.str() << endl; // and reformatted numbers else // otherwise, print the name and bad numberscerr << "input error: " << entry.name<< " invalid number(s) " << badNums.str() << endl;} return os;}static void ioString4(){ vector<PersonInfo> vec = getData(cin);processOS(cout, vec); }

【引用】

代碼 https://github.com/thefistlei/cplusprimer/blob/main/cprimer/cprimer/ioTest.h

總結

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