NSArray到C数组 [英] NSArray to C array

问题描述

我们可以将NSArray转换为c数组。如果没有什么替代品有那里。[假设我需要在opengl函数中提供c数组，其中c数组包含从plist文件读取的顶点指针]

can we convert NSArray to c array. if not what alternatives are there.[suppose i need to feed the c array in opengl functions where the c array contains vertex pointer read from plist files]

推荐答案

答案取决于C数组的性质。

The answer depends on the nature of the C-array.

如果你需要填充一个原始值数组，做这样的事情：

If you need to populate an array of primitive values and of known length, you could do something like this:

NSArray* nsArray = [NSArray arrayWithObjects:[NSNumber numberWithInt:1],
                                             [NSNumber numberWithInt:2],
                                             nil];
int cArray[2];

// Fill C-array with ints
int count = [nsArray count];

for (int i = 0; i < count; ++i) {
    cArray[i] = [[nsArray objectAtIndex:i] intValue];
}

// Do stuff with the C-array
NSLog(@"%d %d", cArray[0], cArray[1]);

这里有一个例子，我们要从 NSArray ，将数组项目保留为Obj-C对象：

Here's an example where we want to create a new C-array from an NSArray, keeping the array items as Obj-C objects:

NSArray* nsArray = [NSArray arrayWithObjects:@"First", @"Second", nil];

// Make a C-array
int count = [nsArray count];
NSString** cArray = malloc(sizeof(NSString*) * count);

for (int i = 0; i < count; ++i) {
    cArray[i] = [nsArray objectAtIndex:i];
    [cArray[i] retain];    // C-arrays don't automatically retain contents
}

// Do stuff with the C-array
for (int i = 0; i < count; ++i) {
    NSLog(cArray[i]);
}

// Free the C-array's memory
for (int i = 0; i < count; ++i) {
    [cArray[i] release];
}
free(cArray);

或者，您可能想要 nil 终止数组而不是传递其长度：

Or, you might want to nil-terminate the array instead of passing its length around:

// Make a nil-terminated C-array
int count = [nsArray count];
NSString** cArray = malloc(sizeof(NSString*) * (count + 1));

for (int i = 0; i < count; ++i) {
    cArray[i] = [nsArray objectAtIndex:i];
    [cArray[i] retain];    // C-arrays don't automatically retain contents
}

cArray[count] = nil;

// Do stuff with the C-array
for (NSString** item = cArray; *item; ++item) {
    NSLog(*item);
}

// Free the C-array's memory
for (NSString** item = cArray; *item; ++item) {
    [*item release];
}
free(cArray);

这篇关于NSArray到C数组的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！