英文:
Replace with "?" all elements in a slice / create a string with ?, for as many elements in a slice
问题
我正在做我的第一个 Golang 作业，所以这可能是一个愚蠢的问题。
我遇到了这样的情况：我需要动态创建一个查询，该查询接受一个参数的数组（切片），因此在执行前需要有相同数量的“？”。
代码如下：
var reportIds []int // 例如 [1, 2, 3, 4]
values := make([]interface{}, 0, len(reportIds))
for key, _ := range reportIds {
values = append(values, reportIds[key])
}
statement, _ :=
database.Prepare("DELETE FROM reports WHERE id IN ({??my_dynamic_question_marks??})")
statement.Exec(values...)
这段代码可以处理参数的值，但我不知道是否有一种简洁的方法来用“？”替换切片中的 n 个元素，以便我可以将其连接成一个字符串。
我提出了这个想法，因为它看起来很简洁，但是只要能够为切片中的每个元素创建一个带有“?, ”的字符串（最后一个元素不带逗号），任何方法都可以。
当然，我可以在 for 循环中实现一个计数器，并动态构建字符串，但我想知道是否有一种更简洁或更“官方”的方法来做到这一点。
英文:
I'm doing my first assignment in Golang, hence this may be silly question.
I have a situation where I need to create a query dynamically that takes an array (slice) of parameters, thus an equal number of "?" pre execution.
Here it is:
var reportIds []int // eg [1, 2, 3, 4]
values := make([]interface{}, 0, len(reportIds))
for key, _ := range reportIds {
values = append(values, reportIds[key])
}
statement, _ :=
database.Prepare("DELETE FROM reports WHERE id IN ({??my_dynamic_question_marks??})")
statement.Exec(values...)
It works for the values but I cannot understand whether there is a clean way of replacing a n number of elements in a slice with "?" so that I could then join it into a string.
I came up with this idea since it seems clean but any way of creating a string with "?, " for as many elements in the slice would work (natually the last one without comma).
I could do that implementing a counter in the for loop of course and build the string dynamically but I was wondering whether there a cleaner or more "official" way of doing it
答案1
得分: 2
你可以构建一个由"?"字符串组成的切片，然后使用strings.Join将它们连接在一起，strings.Join接受一个字符串切片和一个分隔符：
var reportIds []int // 例如 [1, 2, 3, 4]
values := make([]interface{}, len(reportIds))
placeHolders := make([]string, len(reportIds))
for idx, reportID := range reportIds {
values[idx] = reportID
placeHolders[idx] = "?"
}
strings.Join(placeHolders, ",") // => "?,?,?,?"
英文:
You can build a slice of "?" strings, and then join them together with strings.Join, which accepts a slice of strings and a delimiter:
var reportIds []int // eg [1, 2, 3, 4]
values := make([]interface{}, len(reportIds))
placeHolders := make([]string, len(reportIds))
for idx, reportID := range reportIds {
values[idx] = reportID
placeHolders[idx] = "?"
}
strings.Join(placeHolders, ",") // => "?,?,?,?"
通过集体智慧和协作来改善编程学习和解决问题的方式。致力于成为全球开发者共同参与的知识库，让每个人都能够通过互相帮助和分享经验来进步。
评论