Why does NSMutablearray keep returning null?

Question

I am generating a random equation say like 2*3+4..... and using DDMathparser to evaluate it. Here I have a class method which is supposed to return a random equation(stored inside a mutable array) only if it evaluates to a integer. however it keeps returning Null and i can't figure out why. Please help me out.!

#import "Equation.h"
#import "DDMathParser.h"

@implementation Equation
-(NSMutableArray*)randEquation{
    NSMutableArray* usableEquation=[[NSMutableArray alloc]init];
    while(1){
    NSArray *nums = @[@"1", @"2", @"3", @"4", @"5",@"6",@"7",@"8",@"9"];
    unsigned index1=arc4random()%9;
    NSString* num = [NSString stringWithFormat:@"%@", [nums objectAtIndex:index1]];
    NSArray *symbols = @[@"+", @"-", @"*", @"/"];
    unsigned index=arc4random()%4;
    NSString* symb = [NSString stringWithFormat:@"%@", [symbols objectAtIndex:index]];
        NSMutableArray *arrayOfSymbolsAndNumbers = [[NSMutableArray alloc] init];
        for( int i=0;i<=10;i++){
            if (i%2==0) {
                [arrayOfSymbolsAndNumbers addObject:num];
            }
            else{
                [arrayOfSymbolsAndNumbers addObject:symb];
            }

        }
        NSMutableString *stringOfSymbolsAndNumbers=[[NSMutableString alloc]init];
        for (NSObject * obj in arrayOfSymbolsAndNumbers)
        {
            [stringOfSymbolsAndNumbers appendString:[obj description]];


        }
        usableEquation=arrayOfSymbolsAndNumbers;
        NSNumber *result=[stringOfSymbolsAndNumbers numberByEvaluatingString];
        float resultFloat = [result floatValue];
        float checker=resultFloat;
        if (floor(checker)==checker) {
            break;
        }
        else{
            continue;
        }
    }
    return usableEquation;
}

@end

Answer 1

NSLog(@"The content of array is%@",[equation randEquation]);

Based on your code, for this log to output The content of array is(null) means that equation is nil. Your randEquation (while not efficient) looks ok, the problem is that you haven't created the equation instance when you run the log statement.