如何简化多个嵌套if else语句的代码

Question

I am currently using the following code for comparison but as you can see, I am making tonnes of if else statements. Is there a way to simplify the code and make it more efficient?

getGenderRef: (grammer=nil) ->
  @gender_ref = ""
  gender = this.get('gender')
  if gender? and gender == 'male'
    if grammer == 'he'
      @gender_ref = 'he'
    else if grammer == 'his'
      @gender_ref == 'his'
    else if grammer == 'him'
      @gender_ref == 'him'
  else if gender? and gender == 'female'
    if grammer == 'he'
      @gender_ref = 'she'
    else if grammer == 'his'
      @gender_ref == 'her'
    else if grammer == 'him'
      @gender_ref == 'her'
  else if gender? or gender == null
    if grammer == 'he'
      @gender_ref = 'he/she'
    else if grammer == 'his'
      @gender_ref == 'his/her'
    else if grammer == 'him'
      @gender_ref == 'him/her'

Answer 1

You could use a map

var rules = {
    'female': {
        'he': 'she',
        'his': 'her',
        // ...
    },
    'male': {
        'he': 'he',
        // ...
    },
    'default': {
        'he': 'he/she'
        // ...
    }
};

this.gender_ref = rules[gender ? gender : 'default'][grammer];

It's extensible and can also be dynamically generated from another backend (eg a DB).

Edit (by Linus G Thiel) The same in coffeescript:

rules =
  female:
    he: 'she'
    his: 'her'
    // ...
  male:
    he: 'he'
    // ...
  default:
    he: 'he/she'
    // ...

@gender_ref = rules[gender or 'default'][grammer]

Answer 2

Consider to use a switch-statement

switch (gender) {
  case "1":
    alert("");
    break;
  case "2":
    alert("");
    break;
  case "3":
    alert("");
    break;
  case "4":
    alert("");
    break;
  default:
    alert("default");
    break;
}

Answer 3

Use a multi-dimensional hash table.

grammarByGender = {
    "male": { "he" : "he", "his": "his", "him": "him" },
    "female": {"he" : "she", "his" :"her", "him":"her"},
    "neuter": {"he":"he/she","his":"his/her","him":"him/her"}
}

@gender_ref = grammarByGender[this.get("gender")][grammer]

Answer 4

Use map to cache the possible values. You can extend it at any point and will be able to simplify your method:

var genders = {
    "male" : {
       "he": "he",
       "his": "his",
       "him": "him"
   },
   "female" : {
       "he": "she",
       "his": "her",
       "him": "her" 
   },
   "null": {
      "he": "he/she",
      "his": "his/her",
      "him": "him/her"
   }
}

function getGenderRef (grammer) {
  var gender_ref = "",
      availableGenders = genders[this.get('gender')];

  if (availableGenders) {
      gender_ref = availableGenders[grammer];
  }
}

Answer 5

You could reduse the length a tiny bit as follows:

getGenderRef: (grammer=nil) ->
  @gender_ref = ""
  gender = this.get('gender')
  if gender? and gender == 'male'
    if grammer == 'he'
      @gender_ref = 'he'
    else if grammer == 'his'
      @gender_ref == 'his'
    else if grammer == 'him'
      @gender_ref == 'him'
  else if gender? and gender == 'female'
    if grammer == 'he'
      @gender_ref = 'she'
    else if grammer == 'his' or grammer == 'him'
      @gender_ref == 'her'
  else if gender? or gender == null
    if grammer == 'he'
      @gender_ref = 'he/she'
    else if grammer == 'his'
      @gender_ref == 'his/her'
    else if grammer == 'him'
      @gender_ref == 'him/her'

You can't make it a lot shorter than this, because you have alot of different output options. A swtich / case could be a option, but that would be just as much code.

Another option would be to use a object:

references = {
    'male': {
        'he': 'he',
        'his': 'his',
        'him': 'him'
    },
    'female': {
        'he': 'she',
        'his': 'her',
        'him': 'her'
    },
    'null':{
        'he': 'he/she',
        'his': 'his/her',
        'him': 'him/her'
    }
}
//Access:
gender_ref = references[gender ? gender : 'null'][gender_ref];

Answer 6

It would be easy if you go step-by-step. You would learn how to refactor complex conditions that way.

First, notice that you have a common check in the first if and its subsequent else if s, that is if gender? . You should take that out as a common check and refactor your code as follows:

  if gender?
    ...
  else # if gender == null
    ...

This forms your main if and else clause. You will nest if and switch statements under these. The refactored if/else code is given below:

  if gender?
    if gender == 'male'
      switch grammer
        when 'he' then @gender_ref = 'he'
        when 'his' then @gender_ref = 'his'
        when 'him' then @gender_ref = 'him'
    else if gender == 'female'
      switch grammer
        when 'he' then @gender_ref = 'she'
        when 'his' then @gender_ref = 'her'
        when 'him' then @gender_ref = 'her'
  else # if gender == null
    switch grammer
      when 'he' then @gender_ref = 'he/she'
      when 'his' then @gender_ref = 'his/her'
      when 'him' then @gender_ref = 'him/her'

Switches in Coffeescript can work great for your situation, making the code pretty readable and less complex. You can optimize this further.

---

Here is a simple optimization, where you do the assignment to @gender_ref at the beginning of switch statement (again, taking the common part out):

  if gender?
    if gender == 'male'
      @gender_ref = switch grammer
        when 'he' then 'he'
        when 'his' then 'his'
        when 'him' then 'him'
    else if gender == 'female'
      @gender_ref = switch grammer
        when 'he' then 'she'
        when 'his' then 'her'
        when 'him' then 'her'
  else # if gender == null
    @gender_ref = switch grammer
      when 'he' then 'he/she'
      when 'his' then 'his/her'
      when 'him' then 'him/her'

You can optimize it even further by moving @gender_ref = assignment to the parent if (it's not working in the else clause though ... I wonder why).

Answer 7

In terms of performance there is nothing wrong with if statements. I can't help but wonder if this isn't just about readibility.

Anyway here is another option still using if statements.

@gender_ref = grammer; // male values are the same so use as default

if(  gender == "female" ) {

    if( grammer == 'he' ) @gender_ref = 'she';
    if( grammer == 'his' ) @gender_ref = 'her';
    if( grammer == 'him' ) @gender_ref = 'her';

} else if (  !gender ) { // if not defined

    if( grammer == 'he' ) @gender_ref = 'he/she';
    if( grammer == 'his' ) @gender_ref = 'his/her';
    if( grammer == 'him' ) @gender_ref = 'him/her';
}