c++ - map 插入中没有匹配的成员函数

Question

我有以下两个变量:

static vector<map<uint32_t,vector<uint64_t>>> relations;
static map<uint64_t,map<uint32_t,vector<uint64_t>>> transactions;

uint64_t key1;
uint32_t key2;
uint32_t key3;
// init keys...

我正在尝试从 relations 中复制一个 vector 到 transactions 中:

transactions[key1][key2].push_back(relations[key2][key3]));

但我发现这个错误:

main.cpp:175:26: error: no matching member function for call to 'push_back'
     transactions[key1][key2].push_back(relations[key2][key3]));
     ~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/vector:700:36: note: candidate function not viable: no
  known conversion from 'vector<uint64_t>' to 'const value_type' (aka 'const unsigned long long') for 1st argument
_LIBCPP_INLINE_VISIBILITY void push_back(const_reference __x);
                               ^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/vector:702:36: note: candidate function not viable: no
  known conversion from 'vector<uint64_t>' to 'value_type' (aka 'unsigned long long') for 1st argument
_LIBCPP_INLINE_VISIBILITY void push_back(value_type&& __x);

知道发生了什么吗？

Answer 1

relations[key2][key3]是 vector<uint64_t> ，并且您正在尝试将其添加到 transactions[key1][key2]这是 vector<uint64_t> .

您不能添加 vector<uint64_t>到 vector<uint64_t> .

---

如果您想添加第一个 vector 的内容对于第二个，你需要使用 std::vector::insert :

auto& dst = transactions[key1][key2];
const auto& src = relations[key2][key3];
dst.insert(dst.end(), src.begin(), src.end());