The Complete Solidity Course - Blockchain - Zero to Expert

Exercise - Manipulate The Smart Contract Result: Change the function called getResult in our WelcomeToSolidity contract so that the output returns 15.

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IDE:: Tools provided by an IDE include a text editor, a project editor,  a tool bar, and an output viewer.

IDEs can perform a variety of functions. Notable ones include write code, compile code, debug code, and monitor resources.

Solidity is a curly-bracket language.

It is influenced by C++, Python and JavaScript, and is designed to target the Ethereum Virtual Machine (EVM)

Exercise - Instantiate Pragma Solidity:

1. Create a new solidity file called exercise-assignment

2. Instantiate the version solidity of 0.5.0

3. Bonus: increase the range of the version from 0.5.0 up to 0.6.3

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We are specifying the compiler version of solidity ranging and including from 0.7.0 up to and not including 0.9.0

>= means greater than or equal to...

< less than sign..

If we want to write solidity code we first create a new file and assign the type of data file with .sol

Pragma is generally the first line of code within any Solidity file.

Pragma is a directive that specifies the compiler version to be used for current Solidity file.

Solidity is a new language and is subject to continuous improvement on an on-going basis.

Solidity: Solidity is a contract-oriented, high-level language for implementing smart contracts. It was influenced by C++, 

Python and JavaScript and is designed to target the Ethereum Virtual Machine (EVM).

Exercise - Write Variables

1. Create a new variable called wallet as an integer

2. Create a boolean called spend

3. Create a string give it the name notifySpend

4. Initialize the wallet to 500

5. Set the value of spend to false

6. Add the string literal (the string value ) 'you have spent money' to notifySpend

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While writing program in any language, you need to use various variables to store various information.

Variables are nothing but reserved memory locations to store values.

This means that when you create a variable you reserve some space in memory.

Variables: Variables are used to store information to be referenced and manipulated in a computer program. Pseudo code example of storing information into variables

store-owner = 300 - integer

chocolate-bar = 10  - integer

totalValue = store-owner + chocolate-bar = 310

totalValue = 310 - integer

Types: Boolean - Keyword: bool - Value: true/false

Integer - Keyword - uint - Value - Signed and unsigned integers of varying sizes

String - Keyword - string - data values that are made up of ordered sequences of characters

Exercise - Write Your First Function (Calculator)

1. Create a function in the learnFunctions contract called multiplyCalculator

2. Add two parameters to the function a & b and set them as integers.

3. Grant the function public visibility as well as viewing capability for the IDE.

4. Return an integer for the function

5. Create a variable result that contains the logic to multiply a and b

6. Return the result

7. Compile and deploy your very first dApplication and test out the results!!

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FUNCTIONS:

A function is a group of reusable code which can be called anywhere in your program.

This eliminates the need of writing the same code again and again.

It helps programmers in writing modular codes. Functions allow a programmer

to divide a big program into a number of small and manageable functions.

Like any other advanced programming language, Solidity also supports all the features necessary to write modular code using functions. This section explains how to write your own functions in Solidity.

Exercise in DeFi! :)

1. Create a stakingWallet variable as an integer and set it to the value of 10

2. Write a function called airDrop which has public visibility, is IDE viewable and returns an integer

3. create decision making logic so that if the wallet has a value of 10 then add to the wallet 10 more

4. add an else statement so that if the wallet does not equal the value of 10 to add only 1 more

5. return the value of the wallet

6. deploy the contract the test the results - try changing the value of the wallet to 6 and redeploying for varying results

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While writing a program, there may be a situation when you need to adopt one out of a given set of paths.

In such cases, you need to use conditional statements that allow your program to make correct decisions and perform right actions. If statement: The if statement is the fundamental control statement that allows

Solidity to make decisions and execute statements conditionally.

If...else statement: The 'if...else' statement is the next form of control statement that allows

Solidity to execute statements in a more controlled way.

ARITHMETIC EXERCISES

  1. a + b - b + a = ?

  2. a * b * b - 1 = ?

  3. b + b++ + a++ = ?

4. (b % a) + 3 = ?

Exercise - Operations and Operators

1. Create a contract called final exercise (Final Exercise)

2. Initialize 3 state variables a, b, f

3. Assign each variable the following: a should equal 300, b should equal 12, and f should equal 47

4. Create a function called finalize that is public and viewable which returns a local variable d

6. Initialize d to 23

7. Return d in short handed assignment form to multiply itself by itself and then subtracted by b

8 bonus make the function conditional so that it will only return the multiplication if a is greater than or equal to a and b is less than f otherwise d should return 23

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An operator in a programming language is a symbol that tells the compiler or interpreter to perform specific mathematical, relational or logical operation and produce final result.

Exercise - Looping Practice

1. Create a contract myLoopingPracticeContract and place all the following code within:

2. Create a list that ranges from 1 to 20 called longList

3. Create a list called numbersList of the following numbers: 1, 4, 34, 56

4. Create a function that loops through numbersList and returns a true value if the number that the user inputs exists in the list otherwise it should return false.

5. Create a function that loops trhough and returns how many even numbers there are in the long list

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Loops in Solidity allow you to iterate through data and take functional action depending on the data.

A "For" Loop is used to repeat a specific block of code a known number of times.

Exercises with Strings:

    1. Create a string called favoriteColor

    2. Set the favorite color of the string favoriteColor to blue

    3. Create a function which returns the string literal of favoriteColor

    4 . Create a function which changes the favoriteColor string literal from blue to your favorite color.

    5 . Create a function which can return how many characters there are in the string favorite color

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Solidity supports String literal using both double quote (") and single quote ('). It provides string as a data type to declare a variable of type String.

Values that are made up of ordered sequences of characters, such as "hello world". A string can contain any sequence of characters, visible or invisible, and characters may be repeated.

Exercise for Constructors:

1. Create a contract called Base which stores full accessible (inside and outside) data upon deployment

2. Create a contract called Derived which derives the data from base and runs a function that always outputs the data to the integer 5.

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Constructor is a special function using constructor keyword. It initializes state variables of a contract.

Following are key characteristics:

    1. A contract can have only one constructor.

    2. A constructor code is executed once when a contract is created and it is used to initialize contract state.

    3. After a constructor code executed, the final code is deployed to blockchain.

    This code include public functions and code reachable through public functions.

    Constructor code or any internal method used only by constructor are not included in final code.

    A constructor can be either public or internal.

    A internal constructor marks the contract as abstract.

    In case, no constructor is defined, a default constructor is present in the contract.

Exercise Arrays - Create a function that can fully remove an item from an array

1. Create an Empty array called changeArray

2. Create a function called removeElement which sets the index argument of the array to the last element in the array

3. Remove the last index from that function with the pop method

4. Create a function called test which pushes 1 2 3 4 into changeArray

5. Remove the element 2 from the array when the contract is called

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WHAT ARE ARRAYS? :)

Arrays in Solidity is a data structure, which stores a fixed-size sequential collection of elements of the same type.

An array is used to store a collection of data, but it is often more useful to think of an array as a collection of variables of the same type.

Exercise - Enums

1. Create an enum for the color of shirts called shirtColor and set it to the options of either RED or WHITE or BLUE

2. Create a data of shirtColor called defaultChoice which is a constant set to the color BLUE

3. Create a data of shirtColor called choice and don't initiate the value

4. Create a function called setWhite which changes the shirt color of shirtColor to white

5. Create a function getChoice which returns the current choice of shirtColor

6. Create a function getDefaultChoice which returns the default choice of shirtColor

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Enums restrict a variable to have one of only a few predefined values. The values in this enumerated list are called enums. With the use of enums it is possible to reduce the number of bugs in your code.

Exercise: Structs

1. Create a new movie and set it up so that it updates to the movie in the setMovie function

2. Return the id of the new movie

3. Create a new var called comedy and set up comedy to the datatype Movie

4. Update the setMovie function with a comedy movie that contain name, director, and an id

5. Return the movie id of the comedy.

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Structs in Solidity are types that are used to represent a record.

Mapping Assignment:

1. Create a unique data type as a struct called Movie and give it the string properties: title and diretor.

2. Create a map called movie which takes a uint as a key and Movie as a value .

3. Create a function called addMovie which takes three inputs, movie id, title and director which assigns a value of an integer to a movie added back to the movie map. It should include a title and director name.

4. Deploy the contract and update the movie information to the movie map with our favorite movies!

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Mapping is a reference type as arrays and structs. Following is the syntax to declare a mapping type.

Mapping allows you to save data and add a key that you specifiy and then retrieve that info later.

Similar to struct or an array  -  it is a reference type in Solidity you can't iterate through a map - you need to store the keys in an array and you can't give size