CODEWITHSUNDEEP
c++
Yelow Sea
Yelow Sea

Reputation: 45

How to convert list element to string?

I have a try to binding data to textblock in vs 2013.

But I got some problem when I am try to convert list item to string.

this is the error message from vs :

no instance of constructor "std::basic_string<_Elem, _Traits,
_Alloc>::basic_string [with _Elem=wchar_t,
_Traits=std::char_traits<wchar_t>, _Alloc=std::allocator<wchar_t>]"
matches the argument list argument types are:
(std::_List_iterator<std::_List_val<std::_List_simple_types<std::string>>>)

this is my code :

list <string> c1;

//Insert Data
c1.push_back("one");
c1.push_back("two");
c1.push_back("three");
c1.push_back("Four");
c1.push_back("Five");
c1.push_back("Six");
c1.push_back("Seven");
c1.push_back("Eight");
c1.push_back("Nine");
c1.push_back("Ten");




//Random data from list

int RandNum = 0 + (std::rand() % 10);

auto en = c1.begin();
advance(c1.begin(), RandNum);

std::wstring s1(*en);

std::string s2(*en);

ENTEXT->Text = s2; //ENTEXT is textblock name

I am try to pass list element to textblock, but this code shows

error C2664 : 'void Windows::UI::Xaml::Controls::TextBlock::Text::set(Platform::String ^)' : cannot convert argument 1 from 'std::string' to 'Platform::String ^'

Upvotes: 3

Views: 10938

Answers (2)

flogram_dev
flogram_dev

Reputation: 42888

  1. You're using the wrong variable: en is the iterator.
  2. You need to dereference the iterator: *en
  3. You accidentally made it a wstring.

Here's what it should be:

std::string s2(*en);

Btw the list elements are already strings, you don't need to convert anything.

To convert a std::string to Platform::String, you need to use the the c_str member function:

ENTEXT->Text = en->c_str();

Upvotes: 3

Marco A.
Marco A.

Reputation: 43662

Since you wrote

"I got some problem when I am try to convert list item to string"

and not specifically wstring, I suppose you meant to dereference the right iterator and have s2 as a normal std::string copy

int RandNum = 0 + (std::rand() % 10);

auto en = c1.begin();
std::advance(en, RandNum); // Make sure to advance the right iterator

std::string s2(*en);

Example

Notice that the above will create a copy of the list element the iterator points to, which, however, is already a std::string (no conversion is needed). You could just use the dereferenced iterator:

std::cout << *en;

In case you really meant the string->wstring conversion (for whatever reason not explained in the question), you could write:

int RandNum = 0 + (std::rand() % 10);

auto en = c1.begin();
std::advance(en, RandNum); // ditto

std::wstringstream ws;
ws << en->c_str();
std::wstring s2 = ws.str();

Example

or, C++11 solution (mind the -stdlib=libc++ support):

//Random data from list

int RandNum = 0 + (std::rand() % 10);

auto en = c1.begin();
advance(en, RandNum);

typedef std::codecvt_utf8<wchar_t> convert_type;
std::wstring_convert<convert_type, wchar_t> converter;
std::wstring converted_str = converter.from_bytes(*en);

Example

Upvotes: 1

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