我对 Objective-C 还是个新手。我想创建一个未知大小的二维数组，以便我可以访问它并添加值。我来自 C++ 背景并查看教程点和示例，例如 Declaring and Initializing 2D array of unknown size in C看起来 C++ 和 Objective C 在创建二维数组方面有相似之处。
我实现了以下示例，但出现错误:
由于未捕获的异常“NSRangeException”而终止应用程序，原因:“* -[__NSArrayM objectAtIndex:]:索引 0 超出空数组的范围”**
我不确定是什么导致了这个错误，如果能帮助我解决这个错误并理解它，我将不胜感激。
-(NSMutableArray *)categoryCk
{
if (!_categoryCk)
{
_categoryCk = [[NSMutableArray alloc] init];
}
return _categoryCk;
}
-(NSMutableArray *)subcategoryCv
{
if (!_subcategoryCv)
{
_subcategoryCv = [[NSMutableArray alloc] init];
}
return _subcategoryCv;
}
-(NSMutableArray *)subcategoryCk
{
if (!_subcategoryCk)
{
_subcategoryCk = [[NSMutableArray alloc] init];
}
return _subcategoryCk;
}
-(NSMutableArray *)outcomeCv
{
if (!_outcomeCv)
{
_outcomeCv = [[NSMutableArray alloc] init];
}
return _outcomeCv;
}
-(NSMutableArray *)outcomeCk
{
if (!_outcomeCk)
{
_outcomeCk = [[NSMutableArray alloc] init];
}
return _outcomeCk;
}
然后循环创建数组:
if([categories count]>0){
for (int i =0; i < categories.count; i++)
{
NSArray* subCategories= [categories[i] objectForKey: @"subCategories"];
NSDictionary *categoryItems = [categories objectAtIndex:i];
NSString *category = [categoryItems objectForKey:@"cv"];
NSLog(@"%@",category);
[self.categoryCv addObject:category];
NSString *categoryNum = [categoryItems objectForKey:@"ck"];
[self.categoryCk addObject:categoryNum];
if ([subCategories count] > 0){
for (int j = 0; j < subCategories.count; j++) {
if (self.subcategoryCv.count <= i) {
[self.subcategoryCv addObject:[[NSMutableArray alloc] init]];
}
if ([self.subcategoryCv[i] count] <= j) {
[self.subcategoryCv[i] addObject:[[NSMutableArray alloc] init]];
}
if (self.subcategoryCk.count <= i) {
[self.subcategoryCk addObject:[[NSMutableArray alloc] init]];
}
if ([self.subcategoryCk[i] count] <= j) {
[self.subcategoryCk[i] addObject:[[NSMutableArray alloc] init]];
}
NSDictionary *subcategoryItems = [subCategories objectAtIndex:j];
NSString *subCategoryCv = [subcategoryItems objectForKey:@"cv"];
[self.subcategoryCv[i][j] addObject:subCategoryCv];
NSString *subCatNum = [subcategoryItems objectForKey:@"ck"];
[self.subcategoryCk[i][j] addObject:subCatNum];
NSArray* outcome =[[subCategories objectAtIndex:j] objectForKey:@"outcomes"];
if ([outcome count] > 0) {
for (int k = 0; k < outcome.count; k++) {
if (self.outcomeCv.count <= j) {
[self.outcomeCv addObject:[[NSMutableArray alloc] init]];
}
if ([self.outcomeCv[j] count] <= k) {
[self.outcomeCv[j] addObject:[[NSMutableArray alloc] init]];
}
if (self.outcomeCk.count <= j) {
[self.outcomeCk addObject:[[NSMutableArray alloc] init]];
}
if ([self.outcomeCk[j] count] <= k) {
[self.outcomeCk[j] addObject:[[NSMutableArray alloc] init]];
}
NSDictionary *outComeItems = [outcome objectAtIndex:k];
NSString *outcomeCategoryCV = [outComeItems objectForKey:@"cv"];
//NSLog(@"%@",outcomeCatCV);
[self.outcomeCv[j][k] addObject:outcomeCategoryCV];
NSString *outCatNum = [outComeItems objectForKey:@"ck"];
[self.outcomeCk[j][k] addObject:outCatNum];
}
}else{
UIAlertController* alert = [UIAlertController alertControllerWithTitle:@"Alert"
message:@"Error loading data from service : Empty Outcomes data"
preferredStyle:UIAlertControllerStyleAlert];
UIAlertAction* defaultAction = [UIAlertAction actionWithTitle:@"OK" style:UIAlertActionStyleDefault
handler:^(UIAlertAction * action) {}];
[alert addAction:defaultAction];
[self presentViewController:alert animated:YES completion:nil];
}
}
} else{
UIAlertController* alert = [UIAlertController alertControllerWithTitle:@"Alert"
message:@"Error loading data from service : Empty Sub-Categories data"
preferredStyle:UIAlertControllerStyleAlert];
UIAlertAction* defaultAction = [UIAlertAction actionWithTitle:@"OK" style:UIAlertActionStyleDefault
handler:^(UIAlertAction * action) {}];
[alert addAction:defaultAction];
[self presentViewController:alert animated:YES completion:nil];
}
}
}else{
UIAlertController* alert = [UIAlertController alertControllerWithTitle:@"Alert"
message:@"Error loading data from service : Empty Categories data"
preferredStyle:UIAlertControllerStyleAlert];
UIAlertAction* defaultAction = [UIAlertAction actionWithTitle:@"OK" style:UIAlertActionStyleDefault
handler:^(UIAlertAction * action) {}];
[alert addAction:defaultAction];
[self presentViewController:alert animated:YES completion:nil];
}
这就是我尝试访问数组的方式:
cell.textLabel.text = [self.outcomeCv[categoryIndex][subcategoryIndex] objectAtIndex:indexPath.row] ;
最佳答案
当您调用 subcategoryCv[i][j] 时，你必须确保
subcategoryCv.count > i && subcategoryCv[i].count > j
否则，你的问题会崩溃。
为了防止它，你需要添加一个新的NSMutableArray至 subcategoryCv什么时候subcategoryCv.count <= i并添加一个新的 NSMutableArray至 subcategoryCv[i]什么时候subcategoryCv[i].count <= j .
另一个二维数组也是一样。例如 subcategoryCv
if (self.subcategoryCv.count <= i) {
[self.subcategoryCv addObject:[[NSMutableArray alloc] init]];
}
if ([self.subcategoryCv[i] count] <= j) {
[self.subcategoryCv[i] addObject:[[NSMutableArray alloc] init]];
}
NSDictionary *subcategoryItems = [subCategories objectAtIndex:j];
NSString *subCategoryCv = [subcategoryItems objectForKey:@"cv"];
[self.subcategoryCv[i][j] addObject:subCategoryCv];
NSString *subCatNum = [subcategoryItems objectForKey:@"ck"];
[self.subcategoryCk[i][j] addObject:subCatNum];
关于ios - Objective C 创建未知大小的二维数组并访问它，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/47324368/