Flutter：查询AWS AppSync

问题描述

我最近开始使用AWS AppSync＆Flutter。我很难将它们彼此连接。

我正在使用graphql_flutter软件包，但无法弄清楚如何将其用于查询目的。

以下是我的代码段：

g++

我遇到以下错误：

$ cat basic_add.h
#ifndef BASIC_ADD_H_
#define BASIC_ADD_H_

__host__ __device__ int add_test( int a,int b );

#endif
$ cat basic_add.cu
__host__ __device__ int add_test(int a,int b)
{
            return a + b;
}

int my_add_test(int a,int b){ return add_test(a,b);} //wrapper
$ cat add_func.h
#ifndef ADD_FUNC_H_
#define ADD_FUNC_H_

#include <iostream>
#include <math.h>
int my_add_test(int a,int b);
int gpu_main(void);

#endif
$ cat add_func.cu
#include "basic_add.h"
#include <iostream>

// Kernel function to add the elements of two arrays
__global__
void add(int n,float *x,float *y)
{
  int index = blockIdx.x * blockDim.x + threadIdx.x;
  int stride = blockDim.x * gridDim.x;
  printf("gridDim %d,blockDim %d,blockIdx %d,threadIdx %d\n",gridDim.x,blockDim.x,blockIdx.x,threadIdx.x);
  for (int i = index; i < n; i += stride)
  {
    y[i] = add_test(x[i],y[i]);
    printf("blockIdx %d,threadIdx %d,%d\n",threadIdx.x,i);
    break;
  }
}

int gpu_main(void)
{
  int N = 1<<10;
  float *x,*y;

  // Allocate Unified Memory . accessible from CPU or GPU
  cudaMallocManaged(&x,N*sizeof(float));
  cudaMallocManaged(&y,N*sizeof(float));

  // initialize x and y arrays on the host
  for (int i = 0; i < N; i++) {
    x[i] = 1.0f;
    y[i] = 2.0f;
  }

  // Run kernel on 1M elements on the GPU
  int blockSize = 256;
  int numBlocks = (N + blockSize - 1) / blockSize;
  add<<<numBlocks,blockSize>>>(N,x,y);

  // Wait for GPU to finish before accessing on host
  cudaDeviceSynchronize();

  // Check for errors (all values should be 3.0f)
  float maxError = 0.0f;
  for (int i = 0; i < N; i++)
    maxError = fmax(maxError,fabs(y[i]-3.0f));
  std::cout << "Max error: " << maxError << std::endl;

  // Free memory
  cudaFree(x);
  cudaFree(y);

  return 0;
}
$ cat main.cpp
#include <iostream>
#include <math.h>
#include "add_func.h"

int main(void)
{
          gpu_main();
          int a = my_add_test(1,2);
          std::cout << a << std::endl;
          return 0;
}
$ nvcc -dc basic_add.cu
$ nvcc -dc add_func.cu
$ nvcc -dlink -o add.dlink.o add_func.o basic_add.o   
$ g++ -c main.cpp
$ g++ main.o add.dlink.o add_func.o basic_add.o -o test -L/usr/local/cuda/lib64 -lcudart
$

我如何使整个工作正常进行？

解决方法

在使用异步方法时，您需要使用Future函数。您可以像this一样更改方法：

 Future<QueryResult> getRepositories(int numOfRepositories) async {
            final HttpLink httpLink = HttpLink(
              uri: 'https://myapi.xyz.com/graphql',);


            final AuthLink authLink = AuthLink(
              getToken: () async => 'Bearer ${globals.token}',);

            final Link link = authLink.concat(httpLink);

            GraphQLClient client = GraphQLClient(link: link,cache: InMemoryCache());

            QueryOptions query = QueryOptions(documentNode: gql(queries.getAll));

            var result = await client.query(query);

           } 
    

您可以从official documentation中了解有关异步编程的更多信息。