10 minutes to make you understand the syntax of objective-c (vs. Java, C + +)

Source: Internet
Author: User
Tags instance method

A lot of programmers who want to develop iOS, or are developing iOS, have done Java or C + + before, when the first time to see OBJECTIVE-C code is a headache, objective-c code in the syntax and Java, C + + has a big difference, Some students will feel like reading the heavenly book. However, the language is interlinked, there are many similarities. The following is a list of the syntax and java,c++ of the objective-c language, so you can easily objective-c the syntax of what's going on.

Let's see what's in the Objective-c header file and the implementation file:

Header file:

The implementation file, similar to the C + +. cpp file:

A comparison of functions

HelloWorld method
Java language:

[CPP]View Plaincopy
    1. Public void HelloWorld (bool ishelloworld) {
    2. Do something?
    3. }

C + + language:

[CPP]View Plaincopy
    1. void HelloWorld (bool ishelloworld) {
    2. Do something?
    3. }

Objective-c language:

[CPP]View Plaincopy
    1. -(void) HelloWorld: (BOOL) ishelloworld{
    2. Do something?
    3. }

The method preceded by a minus sign (-) is an instance method that must be used by an instance of the class to invoke. Corresponding with the + number, which represents the static method of the class, does not need to be instantiated to invoke.

Second, the message.
Message definition: Sends information to an object.
Messages are a mechanism specific to the runtime environment of iOS. Similar to the C++,java class, or an instance that invokes a class or instance. What I'm saying is similar, and their mechanism actually has a big difference.
[Object Message]

[CPP]View Plaincopy
    1. [Object message:param1 withparameter:param2]
    2. NSString *string;
    3. string = [[NSString alloc] initwithstring:@"Hello"];

The above code is similar to the following:
Java/c++:object.message ()
Java/c++:object.message (PARAM1,PARAM2)
String *str;

str = new String ("Hello");

Third, Import
Import "Class.h"
Import <Class.h>
Import <director/Class.h>
This is similar to the C + + include, Java Import

Iv. Property and synthesize

Property Definition: A getter and setter that @property declare for automatic creation of properties variables
Synthesize definition: @Synthesize declaration implements the getter and setter of the property attribute variable.

In interface: @property dataType variableName
In Implementation:synthesiz VariableName

Iv. methods in the header file


[CPP]View Plaincopy
    1. -(ReturnType) method
    2. -(ReturnType) method: (DataType) param1
    3. -(ReturnType) method: (DataType) param1 Withparam: (dataType) param2

Similar to:

[CPP]View Plaincopy
    1. ReturnType method ()
    2. ReturnType Method (param1)
    3. ReturnType Method (PARAM1,PARAM2)

V. Self
Pointer to yourself
[Self Method]

Similar to: C++/java
This.method ();

Vi. inheritance relationships and interface implementations


[CPP]View Plaincopy
    1. Classa:parenta
    2. Classa:parenta<protocol>
    3. ClassA <Protocol>

Similar to:

[CPP]View Plaincopy
    1. ClassA extends Parenta
    2. ClassA extends Parenta implements interface
    3. ClassA Implements Interface

OBJECTIVE-C protocol is similar to C + + and Java interfaces.

Seven, null pointers

ID obj = nil;
NSString *hello = nil;

Nil is equivalent to NULL in Java;

Eight, ID

Objective-c are similar to those in C + + (void*)

Ps:objective-c, like Java, has a run-time environment with the ability to introspect. Objective-c and Java have a lot of different places, in the iOS system, objective-c memory needs to manage, add arc mechanism after the compiler helped objective-c add release released code. Java is managing memory through the garbage collector.

10 minutes to make you understand the syntax of objective-c (vs. Java, C + +)

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