Question

BOOL bl = YES;
BOOL *bl_pointer = &bl;

*bl_pointer = NO;

NSLog(@"bl is %@", bl?@"YES": @"NO");



NSString *st;
st = @"ss";

NSLog(@"%@ is a string", st);

我最近在学习Objective-C并感到困惑：不应该是

*st = @"ss";

像

*bl_pointer = NO;

因为st也是一个指针，比如bl_pointer，或者我错过了什么？

“Objective-C中的所有变量都是指针”是什么意思？

Answer 1

语句“Objective-C中的所有变量都是指针”是错误的。

所有objc对象都在堆上分配，并通过指针引用（这在技术上也是正确的，因为标记指针等等，但它足够好，直到你获得更好的理解）。

原生C类型（例如，整数类型和结构）将被视为在C中。

NSString是一个客观的C对象。因此，你需要一个指针。

// This is a C type -- not an objc object.
BOOL bl = YES;

// This is a pointer to a BOOL, initialized to point to bl
BOOL *bl_pointer = &bl;

// Dereference a pointer to assign NO to what is being pointed to
*bl_pointer = NO;

// NSString is an objc object, and variables must be pointers
NSString *st;

// You are now pointing to a NSString with the value "ss"
// The confusion may be due to the @"" syntax, which just means that
// there is some NSString object, that has the value "ss" and it is
// being assigned to st.  Note, you read about memory management as well.
st = @"ss";

我建议你得到一本很好的入门书，因为这些都是非常基本的问题。

在objective-c中变量之前的星号，它的真正含义是什么？

1 个答案: