Question

Basically, I have 3 delegate methods that have almost the exact same code except for 1 line in each and the parameters. I realize that I can encapsulate a lot of the code to make 3 or 4 lines of code in each method, but I’m wondering if there’s a way to create just 1 method.

Also, the methods being called on tempData have the same method name as the delegate methods below, but they are actually different methods.

- (void)addElement:(NSString *)currentElement FromKeyboard:(NSString *)name {

    UIView *tempView; 
    NSMutableArray *tempViewList;
    EquationData *tempData;    


    if ([name isEqualToString:@"leftEqCellKeyboard"]) {
        tempData = leftData;
        tempViewList = leftEqViewList;
        tempView = equationCell.leftView;
    }

    if ([name isEqualToString:@"rightEqCellKeyboard"]) {
        tempData = rightData;
        tempViewList = rightEqViewList;
        tempView = equationCell.rightView;
    }

    [tempData addElement:currentElement]; // different

    if ([tempViewList count] != 0) 
        [self clearViewsStoredIn:tempViewList];
    [self setUpView:tempView fromArray:tempData.equation toArray:tempViewList];
}

- (void)changeState:(NSString *)stateName FromKeyboard:(NSString *)name {

   UIView *tempView; 
    NSMutableArray *tempViewList;
    EquationData *tempData;    

 if ([name isEqualToString:@"leftEqCellKeyboard"]) {
        tempData = leftData;
        tempViewList = leftEqViewList;
        tempView = equationCell.leftView;
    }

    if ([name isEqualToString:@"rightEqCellKeyboard"]) {
        tempData = rightData;
        tempViewList = rightEqViewList;
        tempView = equationCell.rightView;
    }

    [tempData changeState:stateName]; // different

    if ([tempViewList count] != 0) 
        [self clearViewsStoredIn:tempViewList];

       [self setUpView:tempView fromArray:tempData.equation toArray:tempViewList];

}

- (void)changeCharge:(NSString *)chargeIncrease FromKeyboard:(NSString *)name {

    UIView *tempView;
    NSMutableArray *tempViewList;
    EquationData *tempData;   

if ([name isEqualToString:@"leftEqCellKeyboard"]) {
        tempData = leftData;
        tempViewList = leftEqViewList;
        tempView = equationCell.leftView;
    }

    if ([name isEqualToString:@"rightEqCellKeyboard"]) {
        tempData = rightData;
        tempViewList = rightEqViewList;
        tempView = equationCell.rightView;
    }  
    [tempData changeCharge:chargeIncrease]; // different

    if ([tempViewList count] != 0) 
        [self clearViewsStoredIn:tempViewList];

    [self setUpView:tempView fromArray:tempData.equation toArray:tempViewList];


}

Answer 1

(Perhaps you should check out http://codereview.stackexchange.com)

The “different” part is always of the form [tempData doSomethingOn:aString];, so you can parametrize with the selector “doSomethingOn:”:

-(void)doSomethingOnString:(NSString*)parameter 
              withSelector:(SEL)selector
              fromKeyboard:(NSString*)name 
{
    // The common parts before

    [tempData performSelector:selector withObject:parameter];

    // The common parts after
}

-(void)addElement:(NSString *)currentElement FromKeyboard:(NSString *)name {
    [self doSomethingOnString:currentElement
                 withSelector:@selector(addElement:)
                 fromKeyboard:name];
}

// etc.

See also:

• -performSelector:withObject:
• The “Selector” concept in Objective-C