Sizeof C 整数数组（在 Obj-C 中）
myclass.h:
#define BUTTON_NAVI 41;
#define BUTTON_SETTINGS 42;
#define BUTTON_INFO 43;
myclass.m:
int btnNavi = BUTTON_NAVI;
int btnSettings = BUTTON_SETTINGS;
int btnArray[2] = {btnNavi, btnSettings};
NSLog(@"count = %i", sizeof(btnArray));
[self addToolbarButtons:btnArray];
->日志：计数 = 8
8？！我做错了什么？
在“addToolbarButtons”内部计数为 4...:-(
编辑：
- (void)addToolbarButtons:(int[])buttonIdArray {
NSLog(@"count = %i", sizeof(buttonIdArray));
}
-> 日志：计数 = 4
myclass.h:
#define BUTTON_NAVI 41;
#define BUTTON_SETTINGS 42;
#define BUTTON_INFO 43;
myclass.m:
int btnNavi = BUTTON_NAVI;
int btnSettings = BUTTON_SETTINGS;
int btnArray[2] = {btnNavi, btnSettings};
NSLog(@"count = %i", sizeof(btnArray));
[self addToolbarButtons:btnArray];
-> Log: count = 8
8?! What did I do wrong?
And inside "addToolbarButtons" count is 4... :-(
EDIT:
- (void)addToolbarButtons:(int[])buttonIdArray {
NSLog(@"count = %i", sizeof(buttonIdArray));
}
-> Log: count = 4
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sizeof给出了以字节为单位的大小，8 个字节听起来适合 2 个整数（每个 32 位或 4 个字节）。如果您想要的是数组的长度，您可以执行
sizeof(arr) / sizeof(arr[0])，这将为您提供整个数组的大小除以每个元素的大小。在这种情况下，您将得到8 / 4 == 2，这正是我所期望的。编辑
为了回答你的第二个问题，当你将数组传递给方法时，你实际上是在传递一个指向数组的指针。因此，指针的大小也是 32 位或 4 字节。如果您希望函数知道数组的长度，则还需要将其长度与所述指针一起传递。
sizeofis giving you the size in bytes, 8 bytes sounds right for 2 integers (32-bit or 4 bytes each).If what you want is the length of the array, you can do
sizeof(arr) / sizeof(arr[0])which will give you the size of the entire array divided by the size of each element. In this case you will get8 / 4 == 2, which is what I take it you expect.EDIT
To answer your second question, when you pass the array to the method, you're actually passing a pointer to the array. Hence, the size of the pointer is also 32-bits or 4 bytes. If you want the function to know the length of the array, you need to also pass its length along with said pointer.
sizeof给出数组的大小（以字节为单位）。一个 int 是 4 个字节，因此 2 元素的 int 数组将是 8 个字节。但是，
sizeof不会在您的方法中执行您想要的操作。当 C 数组传递到函数（或方法）时，它实际上是作为指针传递的，并且 sizeof 将返回指针的大小。您应该修改您的方法以采用长度参数：sizeofis giving the size of the array in bytes. An int is 4 bytes, so a 2-element array of ints will be 8 bytes.However,
sizeofwon't do what you want in your method. When a C array is passed into a function (or method), it actually get passed as a pointer, andsizeofwill return the size of a pointer. You should modify your method to take a length parameter:sizeof运算符给出传递给它的内容的大小（以字节为单位）。如果一个int是 4 个字节，那么两个int的数组就是 8 个字节。然而，
sizeof是对变量本身的编译时检查。在运行时，数组的边界是未知的——在定义变量的范围之外也不知道它们。当您声明参数(int[])buttonIdArray时，编译器会将其脱糖为(int *)buttonArray— 它只是一个普通的 int 指针。因此，当您执行sizeof(buttonArray)时，它会告诉您指针的大小，4。因为该语言不会为您跟踪它们的大小，所以使用 C 数组很痛苦。您必须将数组中的元素数量传递给对其进行操作的每个函数和方法。
The
sizeofoperator gives you the size in bytes of the thing you pass to it. If anintis 4 bytes, then an array of twoints is 8 bytes.However,
sizeofis a compile-time check on the variable itself. At runtime, the bounds of an array are not known — nor are they known outside the scope where the variable was defined. When you declare the argument(int[])buttonIdArray, the compiler desugars that to(int *)buttonArray— it's just a plain int pointer. So when you dosizeof(buttonArray), it tells you the size of a pointer, 4.Because the language doesn't keep track of their size for you, using C arrays is a pain. You have to pass the number of elements in the array to every function and method that acts on it.