Question

for ( tempI = 0; tempI < 10; tempI++ )  
{
    tempJ = 1;
    NSArray *objectsForArray = [NSArray arrayWithObjects:@"array[tempI][tempJ]", @"array[tempI][tempJ+1]",  @"array[tempI][tempJ+2]", nil];
}

我可以像上面那样编写代码吗？我需要在(array[][])中存储浮点值NSArray。我可以这样做吗？我的问题是，我有一个矩阵

1.0   0.4   0.3   0.5  
2.0   0.4   0.5   0.5  
3.0   4.3   4.9   0.5

我需要使用1.0,2.0 3.0检索值（0.4,0.3,0.5）。我怎样才能使用NSDictionary呢？谢谢

for( tempI = 0; tempI < 5; tempI++)
{
        NSDictionary *dictionary[tempI] = [ [NSDictionary alloc] initWithObjects:@"array[tempI][tempI + 1]", @"array[tempI][tempI + 2]", @"array[tempI][tempI + 3]", @"array[tempI][tempI + 4]", @"array[tempI][tempI + 5]", nil];
}

我可以这样写吗？ Objective C是否接受它？

我收到错误

error: variable-sized object may not be initialized

Answer 1

NSArray只能存储对象而不是基元，幸运的是，NSNumber类有一个方便的方法，它接受一个float原语并返回一个float对象：

+ (NSNumber *)numberWithFloat:(float)value

因此您可以像这样填充数组：

float exampleFloat = 5.4;

NSArray *anArrayOfFloatObjects = [NSArray arrayWithObjects:
                                    [NSNumber numberWithFloat:10.0],
                                    [NSNumber numberWithFloat:2],
                                    [NSNumber numberWithFloat:4],
                                    [NSNumber numberWithFloat:exampleFloat],
                                    nil]; // Don't forget the nil to signal
                                          // end of the array

至于你的具体问题，你可以写：

NSMutableArray *tmpArray; // this is necessary since an NSArray can only be initialized 
                          // once and we will need to have all the objects that will be 
                          // added to the array available to us at once.

tmpArray = [NSMutableArray arrayWithCapacity:12]; // returns an autoreleased empty array


for (int col=0; col<=3; col++) {
    for (int row=0; row<=2; row++) {
        [tmpArray addObject:[NSNumber numberWithFloat:array[col][row]]];
    }
}
NSArray *myArray = [NSArray arrayWithArray:tmpArray];

就使用字典来检索矩阵值而言，我能想到的唯一方法是将矩阵值键入代码：

A1 A2 A3 A4

B1 B2 B3 B4

C1 C2 C3 C4

D1 D2 D3 D4

例如：

 NSMutableDictionary *myDictionary;

[myDictionary setObject:[NSNumber numberWithFloat:5.0] forKey:@"A1"];

...

NSNumber *myFloat = [myDictionary objectForKey:@"A1"];

此外，重要的是要指出，无论何时以@“some here”格式编写某些内容，它实际上都是一个NSString对象。所以当你写：

NSArray *objectsForArray = [NSArray arrayWithObjects:
                                             @"array[tempI][tempJ]",
                                             @"array[tempI][tempJ+1]",                                                                                                                                            
                                             @"array[tempI][tempJ+2]",
                                             nil];

这与写作完全相同：

NSString *newString = @"Roses are red";    // example strings
NSString *newString1 = @"Violets are blue";
NSString *newString2 = @"array[tempI][tempJ+1]";
NSString *newString3 = @"These are all string objects";

NSArray *objectsForArray = [NSArray arrayWithObjects:
                                             @"array[tempI][tempJ]",
                                             newString2,                                                                                                                                          
                                             @"array[tempI][tempJ+2]",
                                             nil];

Answer 2

尝试：

for ( int tempI = 0; tempI < 10; tempI++ )  
{
    int tempJ = 1;
    fl_tempI = float(tempI);
    NSArray *objectsForArray = [NSArray arrayWithObjects:@"array[fl_tempI][tempJ]", @"array[fl_tempI][tempJ+1]",  @"array[fl_tempI][tempJ+2]", nil];
}

如何在NSArray中存储浮点值？

2 个答案: