Question

我需要根据某些逻辑连接一个字符串，但我无法弄清楚如何去做。

示例：

var filterString: String = ""
var hasFilter: Bool = false

    if let catId = param["catid"] {
        filterString += "cat_id=\(catId)"
        hasFilter = true
    }

    if let subCatId = param["subcatid"] {
        filterString += "sub_cat_id=\(subCatId)"
        hasFilter = true
    }

    if let locationId = param["stateid"] {
        filterString += "location_id=\(locationId)"
        hasFilter = true
    }


    if hasFilter == true {
        query.filters = filterString
    }

只有在我的查询中 ONE 过滤器

时才会有效

例如：query.filters = "location_id=4"

但如果我发生了两个或更多过滤器，我的查询就会破坏，例如：

query.filters = "location_id=4cat_id=3"

如果我有一个以上的过滤器，我需要用这样的AND语句分隔它：

query.filters = "location_id=4 AND cat_id=3"

但我无法弄清楚如何做到这一点，因为我从来不知道过滤器的顺序是什么，或者是否会有一个或多个过滤器开始

修改

我似乎通过以下方式开展工作：

 var filterString: String = ""
    var hasFilter: Bool = false

        if let catId = param["catid"] {
            filterString += "cat_id=\(catId)"
            hasFilter = true
        }

        if let subCatId = param["subcatid"] {
            if hasFilter == true {
            filterString += " AND sub_cat_id=\(subCatId)"
             } else {
             filterString += "sub_cat_id=\(subCatId)"
            }
            hasFilter = true
        }

        if let locationId = param["stateid"] {
         if hasFilter == true {
         filterString += " AND location_id=\(locationId)"
         } else {
          filterString += "location_id=\(locationId)"
          }
            hasFilter = true
        }


        if hasFilter == true {
            query.filters = filterString
        }

Answer 1

一种解决方案是将过滤器放入数组中，然后如果数组不为空，则将数组值与" AND "分隔符合并。

var filters : [String] = []
if let catId = param["catid"] {
    filters.append("cat_id=\(catId)")
}

if let subCatId = param["subcatid"] {
    filters.append("sub_cat_id=\(subCatId)")
}

if let locationId = param["stateid"] {
    filters.append("location_id=\(locationId)")
}

if filters.count > 0 {
    query.filters = filters.joined(separator: " AND ")
}

Answer 2

也许您可以先创建一个数组并附加所有过滤器。之后创建另一个变量以附加数组中的所有值。

Answer 3

使用内联if语句的另一个选项：

    var param = ["catid" : "111", "subcatid" : "222", "stateid" : "333"]

    var filterString = ""

    if let catId = param["catid"] {
        filterString = "cat_id=\(catId)"
    }

    if let subCatId = param["subcatid"] {
        filterString.appendContentsOf(filterString.characters.count > 0 ? " AND sub_cat_id=\(subCatId)" : "sub_cat_id=\(subCatId)")
    }

    if let locationId = param["stateid"] {
        filterString.appendContentsOf(filterString.characters.count > 0 ? " AND location_id=\(locationId)" : "location_id=\(locationId)")
    }

    print(filterString)

    if (filterString.characters.count > 0) {
        query.filters = filterString
    }

Swift根据不同的值连接字符串

3 个答案: