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

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:

Implementation file:

A comparison of functions

HelloWorld method

Java language:

Public void HelloWorld (bool Ishelloworld)
{
do something?
}

C + + language:

void HelloWorld (bool Ishelloworld)
{
do something?
}

Objective-c language:

-(void) HelloWorld: (BOOL) Ishelloworld
{
do something?
}

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 is actually somewhat different.

Example:

[Object message];

[Object message:param1 withparameter:param2];NSString *string; string = [[NSString alloc] initwithstring:@ "Hello"];

The above code is similar to the following:

Java/c++:object.message ()

Java/c++:object.message (PARAM1,PARAM2)

Java/c++:

String *str;

str = new String ("Hello");

Third, Import

Example:

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.

Example:

In interface: @property dataType variableName

In Implementation:synthesiz VariableName

V. Methods in the header file

Example: Declaring a method in a header file

-(returntype) method-(ReturnType) method: (dataType) param1 -(ReturnType) method: (DataType) param1 Withparam: (dataType) param2

Similar to: C/c++/java

ReturnType method ()ReturnType Method (param1)ReturnType Method (PARAM1,PARAM2)

Vi. self pointing to his own pointer

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

Vii. inheritance relationships and interface implementations

Example:

classa:parenta classa:parenta<protocol> ClassA <Protocol>

Similar to: Java:

ClassA extends Parenta ClassA extends Parenta implements interface ClassA implements interface

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

Eight, NULL pointer

ID obj = nil; NSString *hello = nil;

Nil is equivalent to NULL in Java;

Nine, id

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