"Learning iOS Path: object-c error" Collection <__NSArrayM:0xb550c30> was mutated while being enumerated.

Error message:

Cause of Error:

Crashes when the program performs a traversal and modifies the contents of the array at the same time.

Here's how to fix it:

Method 1: define an identical array, iterate over the new array, and modify the original array.

For example:

Nsmutablearray *arraytemp = [@[@ "AA", @ "VV", @ "BB"] mutablecopy]; Nsarray *array = [Nsarray arraywitharray:arraytemp]; for (NSString * str in array) {   if (condition) {      [arraytemp removeobject:str];   }}

Method 2:
Using an extended method of Enumerateobjectsusingblock in the array, use block syntax

-(void) Enumerateobjectswithoptions: (nsenumerationoptions) opts     usingblock: (void (^) (id obj, Nsuinteger idx, BOOL *stop);

The code is as follows:

Create an Array object Nsmutablearray *array =[@[@ "AA", @ "CC", @ "BB", @ "DD"] mutablecopy]; Call this method [array Enumerateobjectsusingblock:                    ^ (id obj, Nsuinteger idx, BOOL *stop) {       //To determine if the element you want to manipulate is the same, Same return Yes      if ([obj isequaltostring:@ "CC"]) {         *stop = yes;                        if (*stop = = yes) {//If yes, delete, or modify the operation.            [Array replaceobjectatindex:idx withobject:@ "CCC"];            [Array removeobject:obj];            }        }        if (*stop) {//operation succeeded. Output Array             NSLog (@ "%@", array);            }  ];

Learning iOS Path: object-c error Collection <__NSArrayM:0xb550c30> was mutated while being enumerated.