如何将一个NSArray数据添加到另一个NSArray字段？

Question

I tought question title is little bit mismatch , can you please see the following explanation...

Currently i am having 2 NSArray's of data:

 NSArray *arr1 = [[NSArray alloc]initWithObjects:@"aa",@"bb",@"1",@"cc", nil];

 NSArray *arr2 = @[self.lbl1, self.lbl2, self.lbl3, self.lbl4];

In 1st Array i got data from server

I need to load those parameters in specific UILabel's in 2nd Array

I am looking O/P is ::

self.lbl1.text = @"aa";

self.lbl2.text = @"bb";

self.lbl3.text = @"1";

self.lbl4.text = @"cc";

Is there any possiblity, can you please help me out..

in ViewController.h

@property (strong, nonatomic)IBOutlet UILabel* lbl1;
@property (strong, nonatomic)IBOutlet UILabel* lbl2;
@property (strong, nonatomic)IBOutlet UILabel* lbl3;
@property (strong, nonatomic)IBOutlet UILabel* lbl4;

in ViewController.m

- (void)viewDidLoad {
[super viewDidLoad];

NSArray *arr1 = [[NSArray alloc]initWithObjects:@"aa",@"bb",@"1",@"cc", nil];
NSArray *arr2 = @[self.lbl1, self.lbl2, self.lbl3, self.lbl4];

for(int i=0;(i<[arr1 count])&&(i<[arr2 count]);i++)
{
    UILabel *label = (UILabel*)[arr2 objectAtIndex:i];
    label.text = (NSString*)[arr1 objectAtIndex:i];
}
NSLog(@"%@,\n %@,\n %@, \n%@",self.lbl1,self.lbl2,self.lbl3,self.lbl4);

}

CRASH like:

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[__NSPlaceholderArray initWithObjects:count:]: attempt to insert nil object from objects[0]'
 *** First throw call stack:

Answer 1

You can't directly do that but you can set arr2 to:

arr2 = @[self.lbl1, self.lbl2, self.lbl3, self.lbl4];

and then

for (UILabel *lbl in arr2) {
    NSInteger i=[arr2 indexOfObject:lbl];
    lbl.text = [arr1 objectAtIndex:i];
}

Answer 2

Store the labels in the arrays, not their text property.

NSArray *arr1 = [[NSArray alloc]initWithObjects:@"aa",@"bb",@"1",@"cc", nil];
NSArray *arr2 = @[self.lbl1, self.lbl2, self.lbl3, self.lbl4];

for(int i=0;(i<[arr1 count])&&(i<[arr2 count]);i++)
{
  UILabel *label = (UILabel*)[arr2 objectAtIndex:i];
  label.text = (NSString*)[arr1 objectAtIndex:i];
}

Checking for count of both like : (i<[arr1 count])&&(i<[arr2 count]) ensures that the app does not crash if somehow the arrays become of different count.

Answer 3

Assuming both arrays have the same size, you can do:

NSArray *arr3 = @[self.lbl1, self.lbl2, self.lbl3, self.lbl4];

for (NSUInteger i = 0; i < arr1.count; i++) {
    arr3[i].text = arr1[i];
}

If the size of the array received from the server may vary, you can use MIN(arr1.count, arr3.count) , ie minimum of the two sizes, so you won't get an out-of-bounds exception:

for (NSUInteger i = 0; i < MIN(arr1.count, arr3.count); i++) {
    arr3[i].text = arr1[i];
}

Answer 4

Short answer: It is Not possible the way you want to do it.

This is because self.lbl1.text is a NSString and not attached to self.lbl1 anymore ( text is a copy property of UILabel). If you change this NSString, you would not change the value of self.lbl1.text

A better approach may be to save only the label, not its value:

NSArray *arr2 = @[self.lbl1, self.lbl2, self.lbl3, self.lbl4];

In this case, you could loop through your array:

for (NSInteger i=0; i < arr2.count && i < arr1.count; i++) {
    ((UILabel*)[arr2 objectAtIndex:i]).text = [arr1 objectAtIndex:i];
}