Objective-C中的Receiver（接收者）是什么？新手困惑求解答

Hey there, since you're new to Objective-C, let's break down the Receiver concept super simply—no jargon overload!

First, let's unpack that definition you came across:

"In Objective-C, you specify the object (known as the receiver of the method) and the message being sent to that object by enclosing the message expression in brackets."

Objective-C is a message-passing language (it's not just "calling functions" like some other languages). Think of it like a real-life conversation:

• The Receiver is the object you're talking to. It's the "who" in "who should do this thing?"
• The message is the task you're asking it to perform (the method name).
• The brackets [] are how you wrap up this request—like tapping someone on the shoulder and giving them a job to do.

Let's use a real code example to make it click #

Take this basic snippet you'll see all the time in Objective-C:

// Create a string object
NSString *myString = @"I'm learning Objective-C!";
// Ask the string to tell us its length
NSUInteger stringLength = [myString length];

Here:

• myString is the Receiver—it's the object we're sending a message to.
• length is the message—we're asking myString to calculate and return its own character length.
• The brackets [] wrap the whole request, which is Objective-C's unique way of saying "send this message to this receiver".

Another example with a custom object #

Let's say we have a Dog class that can bark on command:

// Dog class definition
@interface Dog : NSObject
- (void)bark; // The message we can send to a Dog instance
@end

@implementation Dog
- (void)bark {
    NSLog(@"Woof! Woof!");
}
@end

// Using the Dog class
Dog *myDog = [[Dog alloc] init];
[myDog bark]; // Send the "bark" message to myDog (the Receiver)

When you run [myDog bark], myDog is the Receiver—it gets the "bark" message and executes the code to print the barking sound.

Key takeaways to remember #

• A Receiver is always an object (we can also have class-level receivers for class methods, but let's stick to instance objects for now while you're learning).
• Every time you use brackets [] in Objective-C, the item on the left is the Receiver, and the item on the right is the message you're sending it.
• It's just a fancy name for "the object that's going to carry out the action you're asking for".

内容的提问来源于stack exchange，提问作者Evan Sevy