c ++，“错误：聚合对象应初始化为'{…}'”

Question

When compiling this code I get the error, "Error: initialization with '{...}' expected for aggregate object" at my function calls. I am compiling using Visual Studio 11.

#include <iostream>
#include <string>
#include <array>
using namespace std;

typedef std::array<string, 5> string_t;
string_t centerString(std::array<string, 5> (&tempArray),unsigned short int length);
string_t evenString(std::array<string, 5> (&tempArray),unsigned short int length);

int main(){
    std::array<string, 5> aArray = {"a","aa","aaa","aaaa","aaaaa"};

    std::array<string, 5> evenStr[5] = evenString(aArray,5);
    std::array<string, 5> centerStr[5] = centerStr(aArray,5);
}


 string_t evenString(std::array<string, 5> (&srcArray),unsigned short int length){
     std::array<string, (sizeof(srcArray)/sizeof(srcArray[0]))> trgtArray= {};
     for(unsigned short int x = 0; x < (sizeof(srcArray)/sizeof(srcArray[0]));x++){
         trgtArray[x] = srcArray[x];
         for(unsigned short int y = 0; y < (length-trgtArray[x].length()); y++){
             trgtArray[x] += " ";
         }
     }

     return(trgtArray);
}

 string_t centerString(std::array<string, 5> (&srcArray),unsigned short int length){
     std::array<string, (sizeof(srcArray)/sizeof(srcArray[0]))> trgtArray= {};
     unsigned short int remainder;
     string spacer = "";
     for(unsigned short int x = 0; x < (sizeof(srcArray)/sizeof(srcArray[0]));x++){
         remainder = length - srcArray[x].length();
         if((remainder % 2) == 0){
            trgtArray[x] = srcArray[x];
            for(unsigned short int y = 0; y < (length-srcArray[x].length()); y++){
                trgtArray[x] += " ";
            }
         }else{
             for(unsigned short int z = 0; z < (remainder/2); z++){
                 spacer += " ";
             }
             trgtArray[x] = spacer + srcArray[x] + spacer + " ";
         }
     }

     return(trgtArray);
 }

Answer 1

You are returning temporary reference in centerString

string_t& centerString(std::array<string, 5> (&tempArray),unsigned short int length);

centerStr is array, can't use it as function

std::array<string, 5> centerStr = centerStr(aArray,5);

I guess you mean

std::array<string, 5> centerStr = centerString(aArray,5);

You could try below sample function, just return array out, RVO should kick in.

std::array<string,5> evenString(std::array<string, 5> (&srcArray), unsigned short length){
     std::array<string,5> trgtArray = {};
    //....
     return trgtArray;
}  

std::array<string, 5> evenStr = evenString(aArray,5);
std::array<string, 5> centerStr = centerString(aArray,5);

Answer 2

Don't ever use native arrays, they suck horrifically, and this is one of the ways in which they suck. Basically, this would require that arrays act sanely and they do not. Language-enforced bad basically means that they can't do a whole host of things that you would expect from any other data type, and they're really not worth the time to use when you could just use std::array like a baus sane person.

Use std::array and be grateful that even the Committee accepts the suckage of C arrays.

I, interestingly, note that you did indeed include <array> , but then did not use std::array .