Writing data (set, update, push) in Firebase - Step-by-Step Execution

Process Flow - Writing data (set, update, push)

Start

↓

Choose write method

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set()

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Overwrite data

↓

Confirm write success

↓

End

This flow shows choosing between set, update, and push to write data in Firebase, then performing the write and confirming success.

Execution Sample

Firebase

ref.set({name: 'Alice'});
ref.update({age: 30});
ref.push({score: 100});

This code writes data by overwriting, updating fields, and adding a new child in Firebase.

Process Table

Step	Action	Data Sent	Effect on Database	Result
1	Call set()	{name: 'Alice'}	Overwrite data at ref with {name: 'Alice'}	Data at ref is now {name: 'Alice'}
2	Call update()	{age: 30}	Add/modify 'age' field, keep other fields	Data at ref is now {name: 'Alice', age: 30}
3	Call push()	{score: 100}	Add new child with unique key under ref	New child created with {score: 100}
4	Confirm writes	N/A	All writes succeeded	Database updated successfully

💡 All write operations completed successfully with expected data changes.

Status Tracker

Variable	Start	After set()	After update()	After push()
Database at ref	{}	{name: 'Alice'}	{name: 'Alice', age: 30}	{name: 'Alice', age: 30, newChildKey: {score: 100}}

Key Moments - 3 Insights

Why does set() overwrite all data at the reference?

Because set() replaces the entire data at the reference, as shown in step 1 of the execution_table where previous data is replaced by {name: 'Alice'}.

How does update() differ from set() in modifying data?

update() only changes specified fields without removing others, as seen in step 2 where 'age' is added but 'name' remains.

What does push() do differently compared to set() and update()?

push() creates a new child with a unique key under the reference, adding data without overwriting existing data, shown in step 3.

Visual Quiz - 3 Questions

Look at the execution_table, what is the database content after step 2?

A {name: 'Alice', age: 30}

B {age: 30}

C {name: 'Alice'}

D {}

💡 Hint

Check the 'Effect on Database' and 'Result' columns for step 2 in the execution_table.

At which step does the database get a new child with a unique key?

A Step 1

B Step 2

C Step 3

D Step 4

💡 Hint

Look for the action 'Call push()' in the execution_table.

If you want to replace all data at a reference, which method should you use?

A update()

B set()

C push()

D None of these

💡 Hint

Refer to the explanation of set() in the key_moments and execution_table step 1.

Concept Snapshot

Firebase Writing Data:
- set(): Overwrites all data at a reference.
- update(): Modifies specified fields, keeps others.
- push(): Adds new child with unique key.
Use set() to replace, update() to change fields, push() to add entries.

Full Transcript

This lesson shows how to write data in Firebase using set, update, and push methods. First, set() replaces all data at a location. Then, update() changes or adds specific fields without removing others. Finally, push() adds a new child with a unique key under the reference. Each step changes the database state as shown. Understanding these differences helps manage data safely and effectively in Firebase.