英文:
MongoDB in Go with mgo, operators with bson.M / bson.D always got syntax error
问题
这是一个愚蠢的语法错误，尝试了很多方法，但就是无法让它工作，有人可以帮忙吗？
在Go中使用mgo操作MongoDB，我试图简化使用$ne操作符的方法，代码如下，但一直得到编译时的语法错误：
第15行：convIter := Session.Copy().DB("").C("convs").Find(bson.M {
第16行： "conversationStatus": interface{} {
第17行： bson.M {
第18行： "$ne": "DESTROYED"
第19行： },
第20行： },
第21行：}).Iter()
尝试添加逗号,或者移除逗号，但就是无法让它工作，总是得到以下编译时的语法错误：
mongodb/query.go:16: 语法错误：意外的{，期望逗号或}
mongodb/query.go:20: 语法错误：意外的}，期望表达式
mongodb/query.go:21: 语法错误：意外的}，期望表达式
英文:
It is kind of stupid syntax error, tried tons of ways, just couldn't get it work, someone please help.
MongoDB in Go with mgo, I just tried to simplify use the $ne operator, code like below, but kept getting compile syntax error:
line 15: convIter := Session.Copy().DB("").C("convs").Find(bson.M {
line 16: "conversationStatus": interface{} {
line 17: bson.M {
line 18: "$ne": "DESTROYED"
line 19: },
line 20: },
line 21: }).Iter()
Tried to add comma , remove comma everywhere, just couldn't get it work, always got such compile syntax error like below:
mongodb/query.go:16: syntax error: unexpected {, expecting comma or }
mongodb/query.go:20: syntax error: unexpected }, expecting expression
mongodb/query.go:21: syntax error: unexpected }, expecting expression
答案1
得分: 9
bson.M 是一个映射类型，所以 bson.M{ ... } 是一个映射字面量。如果键值对写在多行中，每行都必须以逗号结尾。详细信息请参见 https://stackoverflow.com/questions/34846848/how-to-break-a-long-line-of-code-in-golang/34848928#34848928
另外，没有"interface"字面量，可以省略它。interface{}类型的值可以包含/封装任何值，包括bson.M值。而且interface{}值的创建是自动的，甚至不需要类型转换。
正确的语法：
convIter := Session.Copy().DB("").C("convs").Find(bson.M{
"conversationStatus": bson.M{
"$ne": "DESTROYED",
},
}).Iter()
类似地，如果使用bson.D类型（它是一个切片），没有以字面量的闭合括号结尾的行必须以逗号结尾，例如：
d := bson.D{
{Name: "fieldA", Value: 1},
{Name: "fieldB", Value: "running"},
}
英文:
bson.M is a map type, so the bson.M{ ... } is a map literal. If key-value pairs are written in multiple rows, each has to end with a comma. For details, see https://stackoverflow.com/questions/34846848/how-to-break-a-long-line-of-code-in-golang/34848928#34848928
Also there is no "interface" literal, drop that. A value of interface{} type can hold / wrap any value, including a bson.M value. And the interface{} value creation is automatic, you don't even need a type conversion.
Correct syntax:
convIter := Session.Copy().DB("").C("convs").Find(bson.M{
"conversationStatus": bson.M{
"$ne": "DESTROYED",
},
}).Iter()
Similarly, if you use the bson.D type (which is a slice), lines not ending with the closing bracket of the literal has to end with a comma, e.g.:
d := bson.D{
{Name: "fieldA", Value: 1},
{Name: "fieldB", Value: "running"},
}
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