在一個循環中解析雲代碼查詢

Question

我試圖做一個解析雲代碼函數，它檢索一個「Score」，但它的級別和所有者，如果它存在，更新並創建它。 我不能讓它在一個循環內部工作，以重複更新或插入分數列表。

下面是我改編自https://parse.com/docs/js_guide#promises-chaining的代碼，它重現了我的問題。

我resultMessage輸出：

{"result":" loop loop "}

而不是

{"result":" loop set 100 find set 200 success find loopset 100 find set 200 success "}

Parse.Cloud.define("example2", function(request, response) { 
 
\t var resultMessage = "" 
 
\t var query = new Parse.Query("ScoreTest"); 
 
\t var test = ["1", "2"]; // Dumb list to loop over. 
 
\t var promise = Parse.Promise.as(); 
 
\t promise = promise.then(function() { 
 
\t \t _.each(test, function(elt) { 
 
\t \t \t resultMessage = resultMessage + " loop "; 
 
\t \t \t query.find().then(function(students) { 
 
\t \t \t \t resultMessage = resultMessage + " set 100 "; 
 
\t \t \t students[0].set("score", 100); 
 
\t \t \t return students[0].save(); 
 
\t \t \t 
 
\t \t \t }).then(function(valedictorian) { 
 
\t \t \t \t resultMessage = resultMessage + " find "; 
 
\t \t \t return query.find(); 
 
\t \t \t 
 
\t \t \t }).then(function(students) { 
 
\t \t \t \t resultMessage = resultMessage + " set 200 "; 
 
\t \t \t students[0].set("salutatorian", 200); 
 
\t \t \t return students[0].save(); 
 
\t \t \t 
 
\t \t \t }).then(function(salutatorian) { 
 
\t \t \t \t \t resultMessage = resultMessage + " success "; 
 
\t \t \t \t \t return Parse.Promise.as(); 
 
\t \t \t \t 
 
\t \t \t }); 
 
\t \t }); 
 
\t }).then(function() { 
 
\t \t response.success(resultMessage); 
 
\t }) 
 
\t 
 
});

Answer 1

也許我是在公佈的代碼引入歧途。可以說這個問題就是這樣：按照一些標準檢索一個對象。如果存在，請修改並保存。如果它不存在，請創建它。在循環中做所有的事情。

讓具有體積小，承諾返回功能做到這一點對每個邏輯位：

// return a promise for a Score matching level and owner. return 
// undefined if one doesn't exist 
function scoreWithOwnerLevel(owner, level) { 
    var query = new Parse.Query("Score"); 
    query.equalTo("owner", owner); 
    query.equalTo("level", level); 
    return query.first(); 
} 

// return a promise for either an existing score or a new one matching 
// level and owner criteria. set its otherValue 
function findOrCreateScore(owner, level, otherValue) { 
    return scoreWithOwnerLevel(owner, level).then(function(score) { 
     if (!score) { 
      var Score = Parse.Object.extend("Score"); 
      score = new Score(); 
      score.set("owner", owner); 
      score.set("level", level); 
     } 
     score.set("otherValue", param.otherValue); 
     return score; 
    }); 
} 

// take a list of owners, levels and one other value. find 
// or create scores for these based on score and level. 
// assign each the other values and save. assume that params 
// of the form [{ owner:'sam', level:2, otherValue:'foo'}, ... etc.] 
function findOrCreateScoresWith(params) { 
    var scores = _.map(params, function(param) { 
     return findOrCreateScore(param.owner, param.level, param.otherValue); 
    }); 
    return Parse.Object.saveAll(scores); 
}