替代if-else语句或更好的方法

Question

There are 4 different user input fields like Multiselect Drop downs on the UI. The user can provide different combinations of input fields to narrow the result set. (Either select all/few options from the multi-select options).

Example: 2 Multiselect options

Multiselect Option A having elements{"10xyz1","11xyz1",...},

Multiselect Option B having elements{"xyz101","abc111",...}

2^2 possible input combinations(Hint: Binary Truth Table ):

1) Select ALL elements from Multiselect Option A && Select ALL elements from Multiselect Option B,

2) Select ALL elements from Multiselect Option A && Select few elements from Multiselect Option B,

3) Select few elements from Multiselect Option A && Select ALL elements from Multiselect Option B,

4) Select few elements from Multiselect Option A && Select few elements from Multiselect Option B

Note: At least one element must be selected from either options

I have used if else statements to implement my logic(I have separate mongo collection for each possible selection, for 4 fields, 16 possible combinations, so 16 mongo collections), but the problem is the code looks very ugly with a lot of if-else statements moreover over if there is one more field added to the UI then I have to check add additional conditional statements.

For now the number of conditional if-else statements is 2^N (Where N is the number of Multiselect drop-down input fields).

Code Snippet:

  private void constructQuery(MongoQuEry query, AnalysisFilter filter) { query.addFilterField("_id.operator", MongoQuEry.OP_EQUALS, "alpha"); query.addFilterField("_id.month_year", MongoQuEry.OP_IN, getListOfMonthYear(filter)); String collectionName; if (filter.getAllMarket() && filter.getAllCmts() && filter.getAllNode() && filter.getAllPackage()) { collectionName = CollectionNames.ME_USAGE_MONTH_YEAR.toString(); } else if (filter.getAllMarket() && filter.getAllCmts() && filter.getAllNode()) { collectionName = CollectionNames.ME_USAGE_MONTH_YEAR_PACKAGE.toString(); query.addFilterField("_id.package", MongoQuEry.OP_IN, filter.getSubscriberPackage()); } else if (filter.getAllMarket() && filter.getAllCmts() && filter.getAllPackage()) { collectionName = CollectionNames.ME_USAGE_MONTH_YEAR_NODE.toString(); query.addFilterField("_id.node", MongoQuEry.OP_IN, filter.getNode()); } else if (filter.getAllMarket() && filter.getAllCmts()) { collectionName = CollectionNames.ME_USAGE_MONTH_YEAR_NODE_PACKAGE.toString(); query.addFilterField("_id.node", MongoQuEry.OP_IN, filter.getNode()); query.addFilterField("_id.package", MongoQuEry.OP_IN, filter.getSubscriberPackage()); } else if (filter.getAllMarket() && filter.getAllNode() && filter.getAllPackage()) { collectionName = CollectionNames.ME_USAGE_MONTH_YEAR_CMTS.toString(); query.addFilterField("_id.cmts", MongoQuEry.OP_IN, filter.getCmts()); } else if (filter.getAllMarket() && filter.getAllNode()) { collectionName = CollectionNames.ME_USAGE_MONTH_YEAR_CMTS_PACKAGE.toString(); query.addFilterField("_id.cmts", MongoQuEry.OP_IN, filter.getCmts()); query.addFilterField("_id.package", MongoQuEry.OP_IN, filter.getSubscriberPackage()); } else if (filter.getAllMarket() && filter.getAllPackage()) { collectionName = CollectionNames.ME_USAGE_MONTH_YEAR_CMTS_NODE.toString(); query.addFilterField("_id.cmts", MongoQuEry.OP_IN, filter.getCmts()); query.addFilterField("_id.node", MongoQuEry.OP_IN, filter.getNode()); } else if (filter.getAllMarket()) { collectionName = CollectionNames.ME_USAGE_MONTH_YEAR_CMTS_NODE_PACKAGE.toString(); query.addFilterField("_id.cmts", MongoQuEry.OP_IN, filter.getCmts()); query.addFilterField("_id.node", MongoQuEry.OP_IN, filter.getNode()); query.addFilterField("_id.package", MongoQuEry.OP_IN, filter.getSubscriberPackage()); } else if (filter.getAllCmts() && filter.getAllNode() && filter.getAllPackage()) { collectionName = CollectionNames.ME_USAGE_MONTH_YEAR_MARKET.toString(); query.addFilterField("_id.market", MongoQuEry.OP_IN, filter.getMarket()); } else if (filter.getAllCmts() && filter.getAllNode()) { collectionName = CollectionNames.ME_USAGE_MONTH_YEAR_MARKET_PACKAGE.toString(); query.addFilterField("_id.market", MongoQuEry.OP_IN, filter.getMarket()); query.addFilterField("_id.package", MongoQuEry.OP_IN, filter.getSubscriberPackage()); } else if (filter.getAllCmts() && filter.getAllPackage()) { collectionName = CollectionNames.ME_USAGE_MONTH_YEAR_MARKET_NODE.toString(); query.addFilterField("_id.market", MongoQuEry.OP_IN, filter.getMarket()); query.addFilterField("_id.node", MongoQuEry.OP_IN, filter.getNode()); } else if (filter.getAllCmts()) { collectionName = CollectionNames.ME_USAGE_MONTH_YEAR_MARKET_NODE_PACKAGE.toString(); query.addFilterField("_id.market", MongoQuEry.OP_IN, filter.getMarket()); query.addFilterField("_id.node", MongoQuEry.OP_IN, filter.getNode()); query.addFilterField("_id.package", MongoQuEry.OP_IN, filter.getSubscriberPackage()); } else if (filter.getAllNode() && filter.getAllPackage()) { collectionName = CollectionNames.ME_USAGE_MONTH_YEAR_MARKET_CMTS.toString(); query.addFilterField("_id.market", MongoQuEry.OP_IN, filter.getMarket()); query.addFilterField("_id.cmts", MongoQuEry.OP_IN, filter.getCmts()); } else if (filter.getAllNode()) { collectionName = CollectionNames.ME_USAGE_MONTH_YEAR_MARKET_CMTS_PACKAGE.toString(); query.addFilterField("_id.market", MongoQuEry.OP_IN, filter.getMarket()); query.addFilterField("_id.cmts", MongoQuEry.OP_IN, filter.getCmts()); query.addFilterField("_id.package", MongoQuEry.OP_IN, filter.getSubscriberPackage()); } else if (filter.getAllPackage()) { collectionName = CollectionNames.ME_USAGE_MONTH_YEAR_MARKET_CMTS_NODE.toString(); query.addFilterField("_id.market", MongoQuEry.OP_IN, filter.getMarket()); query.addFilterField("_id.cmts", MongoQuEry.OP_IN, filter.getCmts()); query.addFilterField("_id.node", MongoQuEry.OP_IN, filter.getNode()); } else { collectionName = CollectionNames.ME_USAGE_MONTH_YEAR_MARKET_CMTS_NODE_PACKAGE.toString(); query.addFilterField("_id.market", MongoQuEry.OP_IN, filter.getMarket()); query.addFilterField("_id.cmts", MongoQuEry.OP_IN, filter.getCmts()); query.addFilterField("_id.node", MongoQuEry.OP_IN, filter.getNode()); query.addFilterField("_id.package", MongoQuEry.OP_IN, filter.getSubscriberPackage()); } query.setCollection(collectionName); query.addGroupByFields("_id.operator", "_id.month_year"); query.addAliasAggregateField("count", MongoQuEry.AGGR_SUM, "subscriber_count"); int order = MongoQuEry.ORDER_ASC; query.addOrderByFields(order, "_id.month_year"); } 

Answer 1

You can create a tree of decisions, by grouping common conditions, for example, if every time A is true you would like to execute the method1(), instead of write this line code on each 'if' where A is true, you can first check if A is true, then execute this common block of code, then check other conditions, like :

instead of Writing:

if(a && b) {
     example.method1();
     example.method2();
     // more code 1
} else if(a && !b) {
     example.method1();
     // more code 2
} else if(!a && b) {
     example.method2();
     // more code 3
} else if(!a && !b) {
     // more code 4
}

you could write:

if(a) {
     example.method1();
     if(b) {
          example.method2();
          // more code 1
     } else {
          // more code 2
     }
} else {
     if(b) {
          example.method2();
          // more code 3
     } else {
          // more code 4
     }
}

Answer 2

Your collection names seems to have a pattern based on the filter fields, if that's the case this approach may work.

Object marketFilter = filter.getAllMarket();
Object cmtsFilter = filter.getAllCmts();
Object packageFilter = filter.getAllPackage();
Object nodeFilter = filter.getAllNodes();


if(marketFilter != null){
    query.addFilterField("_id.market", MongoQuEry.OP_IN, filter.getMarket());
}
.
.
. upto filter N

String collectionName = getCollectionName(marketFilter, ... filter N)

/* 
 create a function getCollectionName(filter1, ... filterN)   
  in this function you can generate collection name by checking which 
  filters are not null.
*/

NOTE :- This approach will work only if your collection names are based on the filters.

Answer 3

How about switch case or IIf expression?

https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/switch

https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/operators/conditional-operator

switch case would be more legible, and separating the if-else contents into functions:

void FunctionName()
{
        collectionName = CollectionNames.ME_USAGE_MONTH_YEAR_NODE_PACKAGE.toString();
        query.addFilterField("_id.node", MongoQuEry.OP_IN, filter.getNode());
        query.addFilterField("_id.package", MongoQuEry.OP_IN, 
        filter.getSubscriberPackage());
}