Question

我无法使ajax上下文工作： -

var msgdata = "";
$.ajax({
  type: "POST",
  url: "players/" + joinplayer + "/joingame.php",
  data: { 
    userID: "<?php echo $_SESSION['username']; ?>",
    gameinfo: JSON.stringify(<?php echo json_encode($_SESSION['profile']['user'], true); ?>)
  },
  context: msgdata,
  success: function(data) {
    msgdata = data;
    $.ajax({
      type: "POST",
      url: "renamejoin.php",
      data: { 
        userID: "<?php echo $_SESSION['username']; ?>",
        joinID: joinplayer
      },
      context: msgdata,
      success: function(data) {
        if (data == "" && msgdata != "") {
          // sucessfully joined a player's game
        } else {
            alert(data);
        }
      },
      error: function() {   
        alert(joinplayer + "'s game is no longer available.");
      }
    });
  },
  error: function() {
    alert(joinplayer + "'s game is no longer available.");
  }
});
if (msgdata == "");
  // start showing games awaiting players again
  gamefeedrefresh;
  timer = window.setInterval(gamefeedrefresh, 2500);
}

msgdata在这个最后的if语句中总是“”。这个问题似乎是一个范围问题，但即使是一个或两个上下文语句都没有区别。

是否可以解决此范围问题？所有建议都表示赞赏。

Answer 1

Ajax请求是异步的，这意味着程序的其余部分将在请求返回之前执行。如果要在请求完成后运行代码，请将其移至success函数体。

您可能还想查看Promise。

Answer 2

如果要在继续阅读脚本之前强制浏览器完成首先执行请求，只需在ajax方法中添加async选项并将其设置为false。

async: false

Answer 3

考虑到异步性后，整体解决方案并不复杂。

主要问题是为错误退出创建函数然后等待第二次成功被触发使用第一个ajax调用的msgdata，它始终在范围内但仅有效关于第二个ajax的成功触发器。

joinfailed函数可以是内联的，这样joinplayer仍然在范围内，但我无法决定将它放在哪个错误上，所以我决定将它保持独立。

$("#gamefeed").on('click', ".chooseGame", function (evnt) {
  $.ajax({
    type: "POST",
    url: "players/" + joinplayer + "/joingame.php",
    data: { 
      userID: "<?php echo $_SESSION['username']; ?>",
      gameinfo: JSON.stringify(<?php echo json_encode($_SESSION['profile']['user'], true); ?>)
    },
    success: function(data) {
      msgdata = data;
      $.ajax({
        type: "POST",
        url: "renamejoin.php",
        data: { 
          userID: "<?php echo $_SESSION['username']; ?>",
          joinID: joinplayer
        },
        success: function(data) {
          if (data != "") {
            joinfailed(joinplayer);
          } else {
            alert(msgdata); // "you joined joinplayer's game"
            // initialise comms and join the game
          }
        },
        error: function() {   
          joinfailed(joinplayer);
        }
      });
    },
    error: function() {
      joinfailed(joinplayer);
    }
  });
});
function joinfailed(joinplayer) {
  alert(joinplayer + "'s game is no longer available.");
  // start showing games awaiting players again
  gamefeedrefresh;
  timer = window.setInterval(gamefeedrefresh, 2500);
}

使用ajax上下文不能解决范围问题

3 个答案: